UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 13D/A

Under the Securities Exchange Act of 1934

(Amendment No. 2)*

Constellium N.V.

(Name of Issuer)

Common Shares, without par value

(Title of class of securities)

NN22035104

(CUSIP Number)

Eleanor Evans

Rio Tinto plc

2 Eastbourne Terrace

London W2 6LG

United Kingdom

+44 (0) 20 7781 2000

(Name, Address and Telephone Number of Person Authorised to Receive Notices and Communications)

with copy to:

Thomas B. Shropshire, Jr.

Linklaters LLP

One Silk Street

London EC2Y 8HQ

United Kingdom

+44 (0) 20 7456 3223

December 16, 2013

(Date of Event which Requires Filing of this Statement)

If the filing person has previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of §§ 240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check the following box.  ¨

Note: Schedules filed in paper format shall include a signed original and five copies of the schedule, including all exhibits.

See § 240.13d-7 for other parties to whom copies are to be sent.

The information required on the remainder of this cover page shall not be deemed to be “filed” for the purpose of Section 18 of the Securities Exchange Act of 1934 (“Act”) or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

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Item 1. Security and Issuer

This Amendment No. 2 to Schedule 13D amends and supplements the statement on Schedule 13D originally filed by Rio Tinto plc (“Rio Tinto”) and Rio Tinto International Holdings Limited (“RTIH”) on June 10, 2013 and amended on November 18, 2013 (as amended and supplemented, the “Schedule 13D”) with the Securities and Exchange Commission (the “SEC”), relating to the Class A ordinary shares, nominal value €0.02 per share (the “Shares”), of Constellium N.V., a Dutch public law company (the “Company”), whose principal executive offices are at Tupolevlaan 41-61, 1119 NW Schiphol-Rijk, the Netherlands.

Item 3. Source and Amount of Funds or Other Consideration

Item 3 of the Schedule 13D is amended and supplemented as follows:

On December 16, 2013, RTIH sold 9,597,560 Shares (including 1,251,847 Shares sold as a result of the exercise by the underwriters of their option to purchase additional shares (the “Purchase Option”)) pursuant to an underwritten offering (the “Offering”). The Shares were sold at a public offering price of $19.80 per Share less the underwriting discount.

Item 5. Interest in Securities of the Issuer

Item 5 of the Schedule 13D is hereby amended and supplemented as follows:

The responses of the Rio Tinto and RTIH to Rows (11) through (13) of the cover pages of this Schedule 13D and the information set forth in Item 3 are hereby incorporated by reference in this Item 5.

On December 16, 2013, RTIH sold 9,597,560 Shares pursuant to the Offering (including 1,251,847 Shares sold pursuant to the Purchase Option), as discussed in the Company’s registration statement on Form F-1 (File No. 333-192680), filed with the SEC on December 5, 2013, as amended, and the underwriting agreement dated as of December 11, 2013 (the “Underwriting Agreement”), among the Company, RTIH, and Goldman, Sachs & Co. Upon completion of the Offering on December 16, 2013, RTIH held 10 Shares, representing 0.0 per cent. of the Company’s outstanding Shares.

The percentage of Shares is based on 104,076,718 outstanding Shares as of December 16, 2013.

In addition, the Shares deemed beneficially owned by each of Rio Tinto and RTIH with respect to which such person (i) has sole voting power, (ii) shares voting power, (iii) has sole dispositive power and (iv) shares dispositive power are listed in the responses to Items 7, 8, 9 and 10, respectively, of the cover page of this Schedule 13D relating to such person.

Except as disclosed in this Schedule 13D, neither of Rio Tinto nor RTIH nor, to the best of their knowledge, any of the persons listed in Schedule A hereto, beneficially owns any Shares or has the right to acquire any Shares.

Except as disclosed in this Schedule 13D, neither of Rio Tinto nor RTIH nor, to the best of their knowledge, any of the persons listed in Schedule A hereto, presently has the power to vote or to direct the vote or to dispose or direct the disposition of any other Shares which they may be deemed to beneficially own.

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Except as disclosed in this Schedule 13D, neither of Rio Tinto nor RTIH nor, to the best of their knowledge, any of the persons listed in Schedule A hereto, has effected any transaction in the Shares during the past 60 days.

To the best respective knowledge of Rio Tinto and RTIH, no other person has the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, the Shares beneficially owned by the Rio Tinto and RTIH.

Item 6. Contracts, Arrangements, Understandings or Relationships with Respect to Securities of the Issuer

Amended and Restated Shareholders Agreement

Following the Offering, RTIH will hold less than 10 per cent. of the total number of outstanding Shares. As a result, RTIH will no longer be entitled to any information rights with respect to the Company or to designate a member of the board of directors of the Company. It is intended that RTIH’s current designee on the Company’s board will remain as a director through the beginning of 2014, until another director is appointed. RTIH will also no longer be entitled to additional consideration pursuant to a separate additional consideration deed with the Company.

Underwriting Agreement

On December 11, 2013, the Company and RTIH entered into the Underwriting Agreement with Goldman, Sachs & Co. with respect the sale of Shares held by RTIH. Closing of the sales occurred on December 16, 2013.

Lock-Up Agreement

In connection with the Offering and pursuant to the Underwriting Agreement, RTIH entered into a lock-up agreement (the “Lock-Up Agreement”) with Goldman, Sachs & Co., pursuant to which RTIH agreed, subject to certain exceptions, not to offer, sell, contract to sell, pledge, grant any option to purchase, make any short sale or otherwise dispose of or agree to dispose of, any of the Shares, or any options or warrants to purchase any Shares, or any securities convertible into, exchangeable for or that represent the right to receive any Shares, for a 45-day period ending on the date that is 45 days after December 11, 2013 (such period, the “Lock-Up Period”), except with the prior written consent of the representatives of the underwriters.

The summaries of the Underwriting Agreement as described in this Item 6 and in Item 5 above, and of the Lock-Up Agreement as described in this Item 6, do not purport to be complete and are qualified in their entirety by reference to such agreements, which are attached to this Schedule 13D as Exhibits H and I, and are incorporated herein by reference.

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Item 7. Materials to be Filed as Exhibits

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SIGNATURES

After reasonable inquiry and to the best of my knowledge and belief, each of the undersigned certifies that the information set forth in this statement is true, complete and correct.

Dated: December 17, 2013

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SCHEDULE A

The response set forth in Schedule A of the Schedule 13D is hereby amended and restated in its entirety with the information below:

Rio Tinto plc

Directors and Executive Officers

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EXHIBIT INDEX

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EXHIBIT A

JOINT FILING AGREEMENT

The undersigned hereby agree that this Schedule 13D, dated June 10, 2013, with respect to the Class A ordinary shares, nominal value €0.02 per share, of Constellium N.V. is, and any further amendments thereto executed by each of us shall be, filed on behalf of each of us pursuant to and in accordance with the provisions of Rule 13d-1(k)(1) under the Securities Exchange Act of 1934, as amended, and that this Agreement shall be included as an Exhibit to the Schedule 13D and each such amendment. Each of the undersigned agrees to be responsible for the timely filing of the Schedule 13D and any amendments thereto, and for the completeness and accuracy of the information concerning itself contained therein. This Agreement may be executed in any number of counterparts, all of which taken together shall constitute one and the same instrument.

IN WITNESS WHEREOF, the undersigned have executed this Agreement as of the 10th day of June, 2013.