FBR Fibria Celulose S.A.

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 August 1, 2017

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.

Publicly-Held Company

Corporate Taxpayer ID CNPJ/MF no. 60.643.228/0001-21

Company Registry (NIRE) 35.300.022.807 | CVM Code No. 12793

NOTICE TO THE MARKET

FIBRIA CELULOSE S.A. (“ Fibria ” or “ Company ”) (B3: FIBR3 | NYSE: FBR), hereby informs its shareholders and the market in general that the Company will issue export credit notes (NCEs), to back the fund raising transaction via capital markets, through the public distribution of Agribusiness Credit Receivable Certificates (CRA) to be issued by RB Capital Companhia de Securitização de Direitos Creditórios do Agronegócio S.A., in the initial amount of R$ 750,000,000.00 (seven hundred and fifty million reais), and such offer may achieve up to R$ 1.012.500.000,00 (one billion, twelve million, five hundred thousand reais), according to the rules of the offer, in accordance with the decision of the Company’s Board of Directors in the meeting held on June 29, 2017.

The transaction’s documents were filed before the Brazilian Securities Commission (CVM) on this date.

São Paulo, August 01, 2017.

Guilherme Perboyre Cavalcanti

Chief Financial and Investor Relations Officer

1