EXHIBIT 99.1

MERCER INTERNATIONAL INC. REPORTS 2004 SECOND QUARTER RESULTS

        NEW YORK, NY, August 9, 2004 — Mercer International Inc. (Nasdaq: MERCS, TSX: MRI.U) today reported results for the second quarter ended June 30, 2004.

Results of Operations — Three Months Ended June 30, 2004

        Total revenues for the three months ended June 30, 2004 increased to €51.8 million from €47.9 million in the comparative period of 2003, primarily because of higher pulp sales. Pulp and paper revenues were €48.5 million in the second quarter of 2004, versus €45.0 million in the comparative period of 2003.

        Costs of pulp and paper sales in the three months ended June 30, 2004 increased to €44.0 million from €41.5 million in the comparative period of 2003, primarily a result of increased pulp sales volumes.

        For the three months ended June 30, 2004, pulp sales increased to €35.3 million from €31.0 million in the same period a year ago. List prices for Northern Bleached Softwood Kraft Pulp ("NBSK") in Europe were approximately €535 ($645) per tonne in the second quarter of 2004, approximately €464 ($580) per tonne in the first quarter of 2004 and approximately €484 ($550) per tonne in the second quarter of last year. The increase in NBSK pulp prices was partially offset by the weakness of the U.S. dollar versus the Euro in the current period. Increased production volumes due to enhanced operational efficiency lead to higher pulp revenues. In the current quarter, pulp sales by volume were 74,841 tonnes, compared to 69,700 tonnes in the comparative period of 2003.

        Pulp sales realizations were €471 per tonne on average in the current quarter, compared to €416 per tonne in the first quarter of 2004 and €445 per tonne in the three months ended June 30, 2003.

        Transportation and other revenues for the pulp operations were €4.4 million in the three months ended June 30, 2004, compared to €2.4 million in the comparative quarter of last year.

        Cost of sales and general, administrative and other expenses for the pulp operations increased to €36.9 million in the three months ended June 30, 2004 from €31.8 million in the comparative period of 2003, primarily as a result of the inclusion of certain non-capitalized expenses of approximately €2.3 million related to the Stendal mill. On average, per tonne fiber costs for pulp production decreased by approximately 2.8% compared to the second quarter of last year. Depreciation for the pulp operations was €5.6 million in the current quarter, versus €5.5 million in the year ago period.

        For the three months ended June 30, 2004, our pulp operations generated operating income of €3.6 million, versus operating income of €2.3 million in the year ago period.

        Paper sales in the three months ended June 30, 2004 were €13.2 million, compared with €14.0 million in the same period of last year. Sales of specialty papers in the three months ended June 30, 2004 were €8.6 million versus €10.5 million in the three months ended June 30, 2003, primarily as a result of a shift in the product mix. For the current quarter, total paper sales volumes were 15,383 tonnes, versus 15,302 tonnes in the comparative period of last year. On average, prices for specialty papers realized in the current quarter decreased slightly, reflecting a shift in the product mix. Average prices for our printing papers decreased by approximately 6.0% reflecting generally weak demand.

        Cost of sales and general, administrative and other expenses for the paper operations in the three months ended June 30, 2004 increased to €15.1 million from €14.9 million in the comparative quarter of 2003, primarily as a result of higher paper sales volumes. Depreciation for the paper operations was €0.6 million in the three months ended June 30, 2004, compared to €0.5 million in the same period last year.

2

        For the three months ended June 30, 2004, our paper operations generated an operating loss of €2.1 million, compared to €1.1 million in the same period of last year.

        For the three months ended June 30, 2004, consolidated general and administrative expenses increased to €7.3 million from €3.9 million in the year ago period, primarily as a result of the inclusion of certain non-capitalized expenses related to the Stendal mill.

        In the three months ended June 30, 2004, we reported a loss from operations of €0.6 million, compared to income from operations of €1.4 million in the same period last year. Interest expense (excluding capitalized interest of €10.4 million relating to the Stendal pulp mill) in the three months ended June 30, 2004 increased to €2.4 million from €2.2 million a year ago, due to higher borrowings resulting primarily from our convertible note issue in October 2003.

        Our 63% owned subsidiary, Zellstoff Stendal GmbH ("Stendal"), had previously entered into variable-to-fixed rate interest swaps to manage the interest risk exposure with respect to approximately €612.6 million under its project loan facility (the "Stendal Loan Facility") relating to our newly constructed 552,000 tonne NBSK pulp mill near Stendal, Germany (the "Stendal project"). In addition, our wholly-owned subsidiary that operates the Rosenthal mill ("Rosenthal") had previously entered into forward interest rate and interest cap contracts in connection with a portion of the indebtedness relating to the Rosenthal mill. In the three months ended June 30, 2004, the marked to market valuation of these interest rate contracts resulted in a net non-cash holding gain of approximately €15.8 million before minority interests, primarily as a result of an increase in long-term interest rates during the period. In the comparable period of 2003, we recorded a net loss of €18.1 million before minority interests on such interest rate contracts.

        Rosenthal had previously entered into two currency swaps to convert all of its long-term indebtedness under its project loan facility into U.S. dollars as well as a currency forward. Stendal had also entered into a currency swap to convert approximately one-half of its indebtedness under its project loan facility into U.S. dollars as well as a currency forward. In the three months ended June 30, 2004, we recorded a net non-cash holding gain of approximately €13.7 million before minority interests on the valuation of these currency derivatives as a result of a weakening of the U.S. dollar versus the Euro and changes in interest rates related to such currencies, versus a net non-cash holding gain of €13.3 million before minority interests on Rosenthal's then outstanding currency derivatives in the year ago period. Stendal did not have any currency derivatives outstanding during the prior period.

3

        In the current quarter, minority interest, representing the two minority shareholders' proportionate interest in the Stendal project, was €(10.2) million, compared to €6.5 million in the comparative period of 2003.

        Our results for the current period include an adjustment of €0.4 million relating primarily to the valuation of certain assets at the paper operations made obsolete as a result of a change in the product mix.

        We reported net income for the three months ended June 30, 2004 of €16.2 million, or €0.94 per basic share and €0.57 per diluted share, versus net income of €0.9 million, or €0.05 per basic and diluted share, a year ago.

        As the Stendal project is currently under construction and because of its overall size relative to our other facilities, management uses consolidated operating results excluding items relating to the Stendal project to measure the performance and results of our operating units. Management believes this measure provides meaningful information for it and securityholders on the performance of our operating facilities for a reporting period. Upon commencement of commercial production, the Stendal project will be evaluated with our other operating units. For the three months ended June 30, 2004, we reported net income of €16.2 million or €0.57 per share on a diluted basis. If we had excluded items relating to the Stendal project by subtracting the gain on derivative financial instruments of €15.8 million on the Stendal interest rate swaps, €14.0 million on the currency swap and currency forward relating to the Stendal Loan Facility and other income of €0.3 million related to the Stendal mill from, and adding minority interest of €10.2 million and general and administrative expenses of €2.3 million relating to the Stendal mill to, the reported net income of €16.2 million, we would have reported a net loss of €1.4 million or €0.08 per share on a diluted basis. For the three months ended June 30, 2003, we reported net income of €0.9 million or €0.05 per share on a diluted basis. If we had excluded items relating to the Stendal project by adding the loss on derivative financial instruments of €17.6 million on the Stendal interest rate swaps and general and administrative expenses of €0.8 million related to the Stendal mill to, and subtracting minority interests of €6.5 million and other income of €0.3 million related to the Stendal mill from, the reported net loss of €0.9 million, we would have reported net income of €12.4 million or €0.74 per share on a diluted basis. This measure has significant limitations as an analytical tool, and should not be considered in isolation, or as a substitute for analysis of our results as reported under generally accepted accounting principles in the United States ("GAAP").

4

        We generated "Operating EBITDA" of €5.7 million in the current period, compared to Operating EBITDA of €7.3 million in the comparative period of 2003. The decrease from the prior period results is primarily as a result of the inclusion of certain non-capitalized expenses of €2.3 million related to the Stendal mill in the current period. Operating EBITDA is defined as income (loss) from operations plus depreciation and amortization. Management uses Operating EBITDA as a benchmark measurement of its own operating results, and as a benchmark relative to its competitors. Management considers it to be a meaningful supplement to operating income as a performance measure primarily because depreciation expense is not an actual cash cost, and varies widely from company to company in a manner that management considers largely independent of the underlying cost efficiency of their operating facilities. In addition, we believe Operating EBITDA is commonly used by securities analysts, investors and other interested parties to evaluate our financial performance.

        Operating EBITDA does not reflect the impact of a number of items that affect our net income (loss), including financing costs and the effect of derivative instruments. Operating EBITDA is not a measure of financial performance under GAAP, and should not be considered as an alternative to net income (loss) or income (loss) from operations as a measure of performance, nor as an alternative to net cash from operating activities as a measure of liquidity. Operating EBITDA has significant limitations as an analytical tool, and should not be considered in isolation, or as a substitute for analysis of our results as reported under GAAP.

        At June 30, 2004, our cash and cash equivalents were €42.2 million, compared to €52.0 million at the December 31, 2003. We also had €20.9 million of cash restricted to pay construction in progress costs payable and €19.1 million of cash restricted in a debt service account, both related to the Stendal project. In addition, we had €26.9 million of cash restricted in a debt service account relating to the Rosenthal mill's project loan facility. At June 30, 2004, we had a working capital deficit of €19.8 million, primarily because we pre-finance certain governmental grants which we expect to receive under a dedicated tranche of the Stendal Loan Facility but, under our accounting policies, do not record these grants until they are received, as well as Stendal construction in progress costs payable for which we had not drawn down under such facility. At June 30, 2004, we qualified for investment grants totaling approximately €100.6 million from the federal and state governments of Germany, of which we expect to receive €74.1 million in 2004 and the balance subsequently. The grants are not reported in our income and reduce the cost basis of the assets purchased when they are received. At June 30, 2004, we had Stendal construction in progress costs payable of €19.8 million which will be paid pursuant to the Stendal Loan Facility in the ordinary course.

5

Results of Operations — Six Months Ended June 30, 2004

        For the six months ended June 30, 2004, revenues increased to €104.8 million from €98.3 million in the prior period, primarily because of higher pulp sales. We generated a loss from operations of €2.5 million in the six months ended June 30, 2004, compared to income from operations of €2.6 million in the six months ended June 30, 2003, primarily as a result of the inclusion of certain non-capitalized expenses of approximately €5.4 million related to the Stendal mill in the current period. We reported a net loss of €2.7 million or €0.16 per diluted share, compared to a net loss of €10.0 million or €0.60 per diluted share for the six months ended June 30, 2003.

Stendal Project Status

        Construction of the Stendal pulp mill was completed substantially on its planned schedule and budget in the last week of July 2004. Such completion means that the construction and installation of equipment and works are essentially finished and operational testing, checks and approvals are occurring so that continuous production from the mill can commence. At the end of July 2004, the mill had all of its requisite permits in place to commence operations and had secured sufficient fiber supplies for the balance of 2004 and into the first quarter of 2005. At July 31, 2004, the mill had filled in excess of 71% of its overall staffing requirements. The balance of the hiring will occur in affiliated activities such as harvesting and transportation and will be completed through 2004 and 2005 as the mill ramps up operations.

        The Stendal mill is currently being supervised by the contractor using Stendal's personnel to operate the mill. Stendal commenced feeding wood chips to the digester at the end of July 2004 and commenced the initial production of pulp. The initial pulp produced was off-grade pulp which was primarily sold into the recycled fiber, corrugated board and similar markets. The mill is currently producing "start-up quality" pulp. The prices realized on the sale of off-grade and start-up quality pulp are lower than the selling price for on-grade NBSK pulp. Under our current start-up plan, we expect Stendal to commence ramping up pulp production and quality so that the Stendal mill will be producing a significant proportion of saleable kraft pulp by the end of the third quarter of 2004. Pursuant to our start up plan, we expect that the mill would be operating at approximately 80% of its design capacity by the end of 2004.

6

        During the start-up period of the Stendal mill, the mill will undergo extensive testing and evaluation to determine whether mechanical completion has occurred and, following several months of start-up operations, whether certain performance requirements have been met, referred to as the "Acceptance Test". The Acceptance Test requires that the mill continuously produces pulp for a 72-hour period in compliance with specified operational, quality and environmental requirements. Following completion of such testing, if the requisite performance requirements are met, we are required to provide the contractor with an acceptance certificate. Once we deliver the acceptance certificate, we assume responsibility for the operation of the mill, subject to the contractor's warranty obligations.

        Under the current start-up plan, we expect that the contractor will shut down the mill for a two or three-week period in October 2004 for the completion of any adjustments, installations and the replacement of any equipment that may be required in order to fulfill its obligations under the construction contract. We also expect that, in the latter part of 2004, the Stendal mill will be shut down for a few days for fine tuning and cleaning so that the contractor may commence trials for the Acceptance Test.

        Our planned start up of the Stendal mill is subject to risks commonly associated with the start up of large greenfield industrial projects which could result in the Stendal mill experiencing operating difficulties or delays in the start-up period and the Stendal mill may not achieve our planned production, timing, quality or cost projections. These risks include, without limitation, equipment failures or damage, errors or miscalculations in engineering, design specifications or equipment manufacturing, faulty construction or workmanship, defective equipment or installation, human error, industrial accidents, weather conditions, failure to comply with environmental and other permits, and complex integration of processes and equipment.

President's Comments

        Mr. Jimmy S.H. Lee, President and Chairman, stated, "Our results for the second quarter of 2004 reflect improving pulp demand and prices and the overall weakness of the U.S. dollar versus the Euro. In the quarter, pulp prices and demand steadily improved with list prices for NBSK pulp in Europe reaching approximately $645 per tonne by the end of the quarter. Such price improvements were, in part, offset by the weakness of the U.S. dollar versus the Euro during the quarter. Markets for our paper products remained generally weak."

7

        He noted: "We are very excited about the completion of the Stendal pulp mill, substantially on time and budget. Our second quarter results included approximately €2.3 million of general and administrative costs relating to the Stendal mill that are not capitalized."

        Mr. Lee added: "The Stendal mill has been started up and it is now producing start-up quality pulp that is being sold. During the start up to date, we have experienced minor difficulties and delays associated with equipment, installation and integration of processes and systems but are generally pleased with the same. Our current expectation is that the Stendal pulp mill should achieve a steady state of saleable pulp production in the fourth quarter of 2004."

        Mr. Lee concluded: "The completion of the Stendal pulp mill and the current firmness shown in pulp markets leaves us well positioned for growth in the remainder of 2004 and into next year."

        In conjunction with this release, Mercer International will host a conference call, which will be simultaneously broadcast live over the Internet. Management will host the call, which is scheduled for Monday, August 9, 2004 at 10:00 AM (EDT). Listeners can access the conference call live and archived over the Internet through a link at the company's web site at http://www.mercerinternational.com or at http://www.firstcallevents.com/service/ajwz407725525gf12.html. Please allow 15 minutes prior to the call to visit the site and download and install any necessary audio software. A replay of this call will be available approximately two hours after the live call ends until August 16, 2004 at 11:59 P.M. (EDT). The replay number is (800) 642-1687, and the passcode is 8398183.

        Mercer International Inc. is a European pulp and paper manufacturing company. To obtain further information on the company, please visit its web site at http://www.mercerinternational.com.

        The preceding includes forward looking statements which involve known and unknown risks and uncertainties which may cause the company's actual results in future periods to differ materially from forecasted results. Among those factors which could cause actual results to differ materially are the following: market conditions, competition and other risk factors listed from time to time in the company's SEC reports.

8

MERCER INTERNATIONAL INC.
CONSOLIDATED BALANCE SHEETS
As of June 30, 2004 and December 31, 2003
(Unaudited)
(Euros in thousands)

Certain reclassifications were made to the prior period results to conform to the current period presentation.

1

MERCER INTERNATIONAL INC.
CONSOLIDATED STATEMENTS OF OPERATIONS AND RETAINED EARNINGS
For the Six Months Ended June 30, 2004 and 2003
(Unaudited)
(Euros in thousands, except per share data)

Certain reclassifications were made to the prior period results to conform to the current period presentation.

2

MERCER INTERNATIONAL INC.
CONSOLIDATED STATEMENTS OF OPERATIONS AND RETAINED EARNINGS
For the Three Months Ended June 30, 2004 and 2003
(Unaudited)
(Euros in thousands, except per share data)

Certain reclassifications were made to the prior period results to conform to the current period presentation.

3

MERCER INTERNATIONAL INC.
BUSINESS SEGMENT INFORMATION
For the Six Months Ended June 30, 2004 and 2003
(Unaudited)
(Euros in thousands)

Certain reclassifications were made to the prior period results to conform to the current period presentation.

4

MERCER INTERNATIONAL INC.
BUSINESS SEGMENT INFORMATION
For the Three Months Ended June 30, 2004 and 2003
(Unaudited)
(Euros in thousands)

Certain reclassifications were made to the prior period results to conform to the current period presentation.

5

MERCER INTERNATIONAL INC.
RECONCILIATION OF PRO FORMA RESULTS
For the Quarters Ended June 30, 2004 and 2003
(Euros in thousands, except per share data)

6

MERCER INTERNATIONAL INC.
COMPUTATION OF OPERATING EBITDA
For the Quarters Ended June 30, 2004 and 2003
(Euros in thousands)

(1)

Operating EBITDA does not reflect the impact of a number of items that affect the company's net income (loss), including financing costs and the effect of derivative instruments. Operating EBITDA is not a measure of financial performance under accounting principles generally accepted in the United States, and should not be considered as an alternative to net income (loss) or income (loss) from operations as a measure of performance, nor as an alternative to net cash from operating activities as a measure of liquidity. Operating EBITDA has significant limitations as an analytical tool, and should not be considered in isolation, or as a substitute for analysis of the company's results as reported under GAAP.

COMPANY SALES BY PRODUCT CLASS AND VOLUME
(Unaudited)

(1)

Excluding intercompany sales of 2,549 tonnes and 3,611 tonnes of pulp and intercompany net sales revenues of approximately €1.2 million and €1.5 million in the six months ended June 30, 2004 and 2003, respectively.

(2)

Excluding intercompany sales of 1,540 tonnes and 1,482 tonnes of pulp and intercompany net sales revenues of approximately €0.8 million and €0.6 million in the three months ended June 30, 2004 and 2003, respectively.

NOTE: One tonne = 1.0160 of one ton.

7

QuickLinks