Form 6-K Fibria Celulose S.A. For: Apr 27

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 6-K

Report of Foreign Private Issuer

Pursuant to Rule 13a-16 or 15d-16 of

the Securities Exchange Act of 1934

Dated April 27, 2016

Commission File Number: 1-15018

Fibria Celulose S.A.

Fidêncio Ramos, 302 — 3rd and (part of) 4th floors

Edifício Vila Olímpia, Torre B, Bairro Vila Olímpia

04551-010, São Paulo, SP, Brazil

(Address of principal executive offices)

(Indicate by check mark whether the registrant files or will file annual reports under cover of Form 20-F or Form 40-F.)

Form 20-F:  x             Form 40-F:  o

(Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(1)):

Yes:  o             No:  x

(Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(7)):

Yes:  o             No:  x

(Indicate by check mark whether the registrant by furnishing the information contained in this Form, the Registrant is also thereby furnishing the information to the Commission pursuant to Rule 12g3-2(b) under the Securities Exchange Act of 1934.)

Yes:  o            No:  x

If “Yes” is marked, indicate below the file number assigned to the registrant in connection with Rule 12g3-2(b):

Fibria Celulose S.A.

Unaudited consolidated interim financial

information at March 31, 2016

and Report on Review of Interim

Financial Information

1

REPORT ON REVIEW OF CONSOLIDATED INTERIM FINANCIAL INFORMATION

To the Board of Directors and Shareholders

Fibria Celulose S.A

São Paulo — SP

Introduction

We have reviewed the accompanying consolidated interim accounting information of Fibria Celulose S.A., for the quarter ended March 31, 2016, comprising the balance sheet at that date and the statements of income and comprehensive income, the statements of changes in equity and cash flows for the three-month period then ended, and a summary of significant accounting policies and other explanatory information.

Management is responsible for the preparation of the consolidated interim accounting information in accordance with the Deliberation CVM 673/11 (which approved accounting standard CPC 21(R1) - Interim Financial Reporting), and International Accounting Standard (IAS) 34 - Interim Financial Reporting issued by the International Accounting Standards Board (IASB).   Our responsibility is to express a conclusion on this interim accounting information based on our review.

Scope of the review

We conducted our review in accordance with Brazilian and International Standards on Reviews of Interim Financial Information (Brazilian audit standard NBC TR 2410, wholly converged to ISRE 2410 — Review of Interim Financial Information Performed by the Independent Auditor of the Entity, respectively).   A review of interim information consists of making inquiries, primarily of persons responsible for financial and accounting matters, and applying analytical and other review procedures.   A review is substantially less in scope than an audit conducted in accordance with Brazilian and International Standards on Auditing and consequently does not enable us to obtain assurance that we would become aware of all significant matters that might be identified in an audit.   Accordingly, we do not express an audit opinion.

Conclusion on the consolidated interim information

Based on our review, nothing has come to our attention that causes us to believe that the accompanying consolidated interim accounting information referred to above has not been prepared, in all material respects, in accordance with Deliberation CVM 673/11 and IAS 34.

São Paulo, April 26, 2016.

BDO RCS Auditores Independentes SS

CRC 2SP 013846/O-1

Eduardo Affonso de Vasconcelos

Accountant — CRC-1SP166001/O-3

Francisco de Paula dos Reis Júnior

Accountant CRC 1 SP 139268/O-6

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Fibria Celulose S.A.

Unaudited consolidated interim balance sheet at

In thousands of Reais

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Fibria Celulose S.A.

Unaudited consolidated interim balance sheet at

In thousands of Reais (continued)

The accompanying notes are an integral part of these unaudited consolidated interim financial information.

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Fibria Celulose S.A.

Unaudited consolidated interim statement of profit or loss

In thousands of Reais, except for the income per shares

The accompanying notes are an integral part of these unaudited consolidated interim financial information.

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Fibria Celulose S.A.

Unaudited consolidated interim statement of comprehensive income

In thousands of Reais, except for the income per shares

The accompanying notes are an integral part of these unaudited consolidated interim financial information.

6

Fibria Celulose S.A.

Unaudited interim statement of changes in shareholders’ equity

In thousands of Reais, unless otherwise indicated

The accompanying notes are an integral part of these unaudited consolidated interim financial information.

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Fibria Celulose S.A.

Unaudited consolidated interim statement of cash flows

In thousands of Reais

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Fibria Celulose S.A.

The accompanying notes are an integral part of these unaudited consolidated interim financial information.

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Fibria Celulose S.A.

Notes to the unaudited consolidated interim
financial information at March 31, 2016

In thousands of Reais, unless otherwise indicated

1                                        Operations and current developments

(a)                                General information

Fibria Celulose S.A. is incorporated under the laws of the Federal Republic of Brazil, as a publicly-held company. Fibria Celulose S.A. and its subsidiaries are referred to in this consolidated interim financial information as the “Company”, “Fibria”, or “we”. We have the legal status of a share corporation, operating under Brazilian corporate law. Our headquarter and principal executive officers are located in São Paulo, SP, Brazil.

We are listed on the stock exchange of São Paulo (BM&FBOVESPA) and the New York Stock Exchange (NYSE) and we are subject to the reporting requirements of the Brazilian Comissão de Valores Mobiliários (CVM) and the United States Securities and Exchange Commission (SEC).

Our activities are focused on the growth of renewable and sustainable forests and the manufacture and sale of bleached eucalyptus kraft pulp. Forests in formation are located in the States of São Paulo, Mato Grosso do Sul, Minas Gerais, Rio de Janeiro, Espírito Santo, Bahia and Rio Grande do Sul.

We operate in a single operating segment, which is the producing and selling of short fiber pulp, with our pulp production facilities located in the cities of Aracruz (State of Espírito Santo), Três Lagoas (State of Mato Grosso do Sul), Jacareí (State of São Paulo) and Veracel (State of Bahia) (jointly- controlled entity).

The pulp produced for export is delivered to customers by sea vessels on the basis of long-term contracts with the owners of these vessels, through the ports of Santos, located in the State of São Paulo (operated under a concession from Federal Government until 2017) and Barra do Riacho, located in the State of Espírito Santo (operated by our subsidiary Portocel - Terminal Especializado Barra do Riacho S.A.).

On December 9, 2015, we participated in the public auction nº 03/2015, promoted by “Agência Nacional de Transportes Aquaviários - ANTAQ”, a regulatory agency, for the leasing of the public areas and infrastructures for handling and storage of paper, pulp and general cargo, for 25 years (renewable for 25 years). The Company was awarded the contract based on its proposal for the Macuco Terminal (STS07), located in the port of Santos, State of São Paulo, in the amount of R$ 115,047, which the approval of the public auction and the adjudication were published in the Federal Official Gazette on March 2, 2016.

With the approval of the result and based on the standards ICPC 01 (R1) / IFRIC 12 - Service Concession Arrangements and OCPC 05 - Concession Contracts, the subsidiary Fibria Terminal de Celulose de Santos SPE S.A., recently incorporated by the Company for the administration of Macuco Terminal, recognized the amount of R$ 115,047 related to the grant concession rights into the group of “Intangible assets”, which will be amortized over the concession period, against an accounting payable for ANTAQ, recorded under “Other payables”, as current liabilities. The payment was made on April 14, 2016.

The main investments according to the contract include:

(i)        a new storage facility, handling and transshipment of cargo equipment, with static capacity of 75,000 tons at least, ensuring the movement of 1,800,000 tons of pulp bales per year; and,

(ii)     the implementation of new railway lines for access to port facilities.

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Fibria Celulose S.A.

Notes to the unaudited consolidated interim
financial information at March 31, 2016

In thousands of Reais, unless otherwise indicated

The startup of the Terminal is expected for the second semester of 2017.

(b)                                Non-current assets held for sale

Losango project assets

On December 28, 2012, the Company and CMPC Celulose Riograndense Ltda. (“CMPC”) signed the definitive Purchase and Sale Agreement for the sale of all of the Losango project assets, comprising approximately 100 thousand hectares of land owned by Fibria and approximately 39 thousand hectares of planted eucalyptus and leased land, all located in the State of Rio Grande do Sul, in the amount of R$ 615 million.

Was received in advance the amount of R$ 477 million, recognized under “Advances received in relation to assets held for sale”. Another installment, amounting to R$ 140 million, was deposited in an escrow account and will be released to us once additional government approvals are obtained. In case of the approvals is not obtained after the period of 96 months, will be returned to CMPC the amount paid to us, plus interest and the escrow deposits made by CMPC will revert.

Since the signing of agreement with CMPC, we have taken action to obtain the approvals needed, such as the fulfillment of all conditions precedent, the partial renewal of the area operating license and filing the documentation required by the government agencies. We are confident that approval will be granted.

We have concluded that these assets should remain classified as “assets held for sale” as non-current assets as at March 31, 2016. However, the completion of the sale is not under our sole control and depends on various government approvals, which have been slower than expected.

The Losango assets did not generate any significant impact in the three-month period ended March 31, 2016 and 2015, since that at this moment, the result of the transaction has not been recognized.

(c)                                 Approval of the expansion plan of the Três Lagoas Unit

On May 14, 2015, the Board of Directors approved the Horizonte 2 Project for the construction of the second Três Lagoas pulp production line.

The Horizonte 2 Project, the construction of which has already started, consists of a new bleached eucalyptus pulp production line with a capacity of 1.85 million tons per year and an estimated investment of US$ 2.2 billion. The startup of the line is projected for the fourth quarter of 2017. Virtually all Horizonte 2 Project supply agreements for delivery and installation of equipment and related services had been contracted.

The Project is being financed from the Company’s operating cash flows and financing agreements under negotiation with financial institutions.

2                                        Presentation of consolidated interim financial information and summary of significant accounting policies

2.1                              Consolidated interim financial information - basis of preparation

The consolidated interim financial information have been prepared under the historical cost convention, as modified by available-for-sale financial assets, other assets and financial liabilities (including

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Fibria Celulose S.A.

Notes to the unaudited consolidated interim
financial information at March 31, 2016

In thousands of Reais, unless otherwise indicated

derivative instruments) measured at fair value.

(a)                                Accounting policies adopted

The consolidated interim financial information has been prepared and is being presented in accordance with IAS 34 and Deliberation 673/11 issued by the Brazilian Securities and Exchange Commission (CVM), which approved the CPC 21(R1) - “Interim Financial Reporting” as issued by the International Accounting Standards Board (IASB) and the Accounting Statements Committee Standards (CPC), and disclose all (and only) the applicable significant information related to the financial statements, which is consistent with the information utilized by management in the performance of its duties.

The consolidated interim financial information should be read in conjunction with the audited financial statements for the year ended December 31, 2015, considering that its purpose is to provide an update on the activities, events and significant circumstances in relation to those presented in the annual financial statements.

The current accounting practices, which include the measurement principles for the recognition and valuation of the assets and liabilities, the calculation methods used in the preparation of this interim financial information and the estimates used, are the same as those used in the preparation of the most recent annual financial statements, except for the items related to the adoption of the new standards, amendments and interpretations issued by IASB and CVM, as detailed in Note 3 below.

(b)                                Approval of the consolidated interim financial information

The consolidated unaudited interim financial information was approved by the Board of Directors on April 26, 2016.

2.2                              Critical accounting estimates and assumptions

Estimates and assumptions are continually evaluated and are based on historical experience and other factors, including expectations of future events that are believed to be reasonable under the circumstances. Accounting estimates will seldom match the actual results. In the three-month period ended March 31, 2016, there were no significant changes in the estimates and assumptions which are likely to result in significant adjustments to the carrying amounts of assets and liabilities during the current period, compared to those disclosed in Note 3 to our most recent annual financial statements.

3                                        New standards, amendments and interpretations issued by IASB and CVM

The standards below have been issued and are effectives for future periods, as from January 1, 2018. We have not early adopted these standards.

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Fibria Celulose S.A.

Notes to the unaudited consolidated interim
financial information at March 31, 2016

In thousands of Reais, unless otherwise indicated

There are no other IFRSs or IFRIC interpretations that are not yet effective that the Company expect to have a material impact on the Company’s financial position and results of operations.

4                                        Risk management

The risk management policies and financial risk factors disclosed in the annual financial statements (Note 4) as at December 31, 2015 did not show any significant changes. The Company’s financial liabilities which present liquidity risk are presented below by maturity (Note 4.1), exchange risk exposure (Note 4.2), sensitivity analysis (Note 5) and fair value estimates (Note 6), which was considered relevant by Fibria’s management to be accompanied quarterly.

4.1                              Liquidity risk

The table below presents the financial liabilities into relevant maturity groupings based on the remaining period from the balance sheet date to the contractual maturity date. The amounts disclosed in the table are the contractual undiscounted cash flows and as such they differ from the amounts presented in the consolidated balance sheet.

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Fibria Celulose S.A.

Notes to the unaudited consolidated interim
 financial information at March 31, 2016

In thousands of Reais, unless otherwise indicated

4.2                              Foreign exchange risk

5                                        Sensitivity analysis

Sensitivity analysis of changes in foreign currency

The evaluation of the Company’s significant risk factor of the U.S. Dollar exposure uses the period of three months, consistent with our policy. We considered as the probable scenario the fair value considering the market yield as at March 31, 2016.

The probable scenario is the closing exchange rate at the date of these consolidated interim financial information (R$ x USD = 3.5589). As the amounts have already been recognized in the consolidated financial statement, there are no additional effects in the Statement of profit or loss in this scenario. In the “Possible” and “Remote” scenarios, the U.S. Dollar is deemed to appreciate/depreciate by 25% and 50%, before tax, when compared to the “Probable” scenario:

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Fibria Celulose S.A.

Notes to the unaudited consolidated interim
financial information at March 31, 2016

In thousands of Reais, unless otherwise indicated

Sensitivity analysis in changes in interest rate

We adopted as the probable scenario the fair value considering the market yield as at March 31, 2016. As the amounts have already been recognized in the consolidated interim financial information, there are no additional effects in the Statement of profit or loss in this scenario. In the “Possible” and “Remote” scenarios, the interest rates are deemed to increase/decrease by 25% and 50%, respectively, before tax, when compared to the “Probable” scenario: