UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 13G

Under the Securities Exchange Act of 1934

(Amendment No. 2)*

Millennial Media, Inc.

(Name of Issuer)

COMMON STOCK, $0.001 PAR VALUE

(Title of Class of Securities)

60040N105

(CUSIP Number)

December 31, 2014

(Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule is filed:

¨ Rule 13d-1(b)

¨ Rule 13d-1(c)

x Rule 13d-1(d)

* The remainder of this cover page shall be filled out for a reporting person’s initial filing on this form with respect to the subject class of securities, and for any subsequent amendment containing information which would alter the disclosures provided in a prior cover page.

The information required in 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).

CUSIP No. 60040N105 13G Page 2 of 11 Pages

1.	NAMES OF REPORTING PERSONS I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY) Deer VI & Co. LLC
2.	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS) (a)  ¨        (b)  x
3.	SEC USE ONLY
4.	CITIZENSHIP OR PLACE OF ORGANIZATION Delaware
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH		5.	SOLE VOTING POWER 6,890,120
		6.	SHARED VOTING POWER -0-
		7.	SOLE DISPOSITIVE POWER 6,890,120
		8.	SHARED DISPOSITIVE POWER -0-
9.	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 6,890,120
10.	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS) ¨
11.	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9 5.0%*
12.	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS) OO

* The percentage of shares beneficially owned as set forth in row 11 above is based on 138,646,259 shares of Common Stock of the Issuer outstanding as of December 8, 2014, as reported in the Issuer’s Registration Statement on Form S-3 filed on December 15, 2014 (the “Form S-3”).

CUSIP No. 60040N105 13G Page 3 of 11 Pages

1.	NAMES OF REPORTING PERSONS I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY) Bessemer Venture Partners Co-Investment L.P.
2.	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS) (a)  ¨        (b)  x
3.	SEC USE ONLY
4.	CITIZENSHIP OR PLACE OF ORGANIZATION Delaware
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH		5.	SOLE VOTING POWER 1,960,298
		6.	SHARED VOTING POWER -0-
		7.	SOLE DISPOSITIVE POWER 1,960,298
		8.	SHARED DISPOSITIVE POWER -0-
9.	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 6,890,120
10.	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS) ¨
11.	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9 5.0%*
12.	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS) PN

* The percentage of shares beneficially owned as set forth in row 11 above is based on 138,646,259 shares of Common Stock of the Issuer outstanding as of December 8, 2014, as reported in the Issuer’s Form S-3.

CUSIP No. 60040N105 13G Page 4 of 11 Pages

1.	NAMES OF REPORTING PERSONS I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY) Bessemer Venture Partners VI Institutional L.P.
2.	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS) (a)  ¨        (b)  x
3.	SEC USE ONLY
4.	CITIZENSHIP OR PLACE OF ORGANIZATION Delaware
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH		5.	SOLE VOTING POWER 85,274
		6.	SHARED VOTING POWER -0-
		7.	SOLE DISPOSITIVE POWER 85,274
		8.	SHARED DISPOSITIVE POWER -0-
9.	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 6,890,120
10.	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS) ¨
11.	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9 5.0%*
12.	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS) PN

* The percentage of shares beneficially owned as set forth in row 11 above is based on 138,646,259 shares of Common Stock of the Issuer outstanding as of December 8, 2014, as reported in the Issuer’s Form S-3.

CUSIP No. 60040N105 13G Page 5 of 11 Pages

1.	NAMES OF REPORTING PERSONS I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY) Bessemer Venture Partners VI L.P.
2.	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS) (a)  ¨        (b)  x
3.	SEC USE ONLY
4.	CITIZENSHIP OR PLACE OF ORGANIZATION Delaware
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH		5.	SOLE VOTING POWER 4,844,548
		6.	SHARED VOTING POWER -0-
		7.	SOLE DISPOSITIVE POWER 4,844,548
		8.	SHARED DISPOSITIVE POWER -0-
9.	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 6,890,120
10.	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS) ¨
11.	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9 5.0%*
12.	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS) PN

* The percentage of shares beneficially owned as set forth in row 11 above is based on 138,646,259 shares of Common Stock of the Issuer outstanding as of December 8, 2014, as reported in the Issuer’s Form S-3.

CUSIP No. 60040N105 13G Page 6 of 11 Pages

Item 1(a). Name of Issuer:

Millennial Media, Inc. (the “Issuer”)

Item 1(b). Address of Issuer’s Principal Executive Offices:

2400 Boston Street, Suite 201, Baltimore, Maryland 21224

Item 2(a). Name of Person Filing:

This statement is being filed by the following persons with respect to the shares (the “Shares”) of common stock (“Common Stock”) of the Issuer directly owned by Bessemer Venture Partners Co-Investment L.P. (“BVP Co-Invest”), Bessemer Venture Partners VI Institutional L.P. (“BVP VI Institutional”) and Bessemer Venture Partners VI L.P. (“BVP VI” and, collectively, the “Funds”).

(a) Deer VI & Co. LLC (“Deer VI”), the sole general partner of each of the Funds;

(b) BVP Co-Invest, which directly owns 1,960,298 Shares;

(c) BVP VI Institutional, which directly owns 85,274 Shares and

(d) BVP VI, which directly owns 4,844,548 Shares.

Deer VI, BVP Co-Invest, BVP VI Institutional and BVP VI are sometimes individually referred to herein as a “Reporting Person” and collectively as the “Reporting Persons.”

Item 2(b). Address of Principal Business Office or, if None, Residence:

The address of the principal business office of each of the Reporting Persons:

c/o Bessemer Venture Partners

1865 Palmer Avenue; Suite 104

Larchmont, NY 10583

Item 2(c). Citizenship:

Deer VI — Delaware

BVP Co-Invest — Delaware

BVP VI Institutional — Delaware

BVP VI — Delaware

Item 2(d). Title of Class of Securities:

Common Stock, par value $0.001 per share

Item 2(e). CUSIP Number:

60040N105

Item 3. Not Applicable.

Item 4. Ownership.

CUSIP No. 60040N105 13G Page 7 of 11 Pages

For Deer VI:

(a) Amount beneficially owned: 6,890,120 shares of Common Stock

(b) Percent of class: 5.0%

(c) Number of shares as to which such person has:

(i) Sole power to vote or to direct the vote: 6,890,120

(ii) Shared power to vote or to direct the vote: —0—

(iii) Sole power to dispose or to direct the disposition of: 6,890,120

(iv) Shared power to dispose or to direct the disposition of: —0—

For BVP Co-Invest:

(a) Amount beneficially owned: 6,890,120 shares of Common Stock

(b) Percent of class: 5.0%

(c) Number of shares as to which such person has:

(i) Sole power to vote or to direct the vote: 1,960,298

(ii) Shared power to vote or to direct the vote: —0—

(iii) Sole power to dispose or to direct the disposition of: 1,960,298

(iv) Shared power to dispose or to direct the disposition of: —0—

For BVP VI Institutional:

(a) Amount beneficially owned: 6,890,120 shares of Common Stock

(b) Percent of class: 5.0%

(c) Number of shares as to which such person has:

(i) Sole power to vote or to direct the vote: 85,274

(ii) Shared power to vote or to direct the vote: —0—

(iii) Sole power to dispose or to direct the disposition of: 85,274

(iv) Shared power to dispose or to direct the disposition of: —0—

CUSIP No. 60040N105 13G Page 8 of 11 Pages

For BVP VI:

(a) Amount beneficially owned: 6,890,120 shares of Common Stock

(b) Percent of class: 5.0%

(c) Number of shares as to which such person has:

(i) Sole power to vote or to direct the vote: 4,844,548

(ii) Shared power to vote or to direct the vote: —0—

(iii) Sole power to dispose or to direct the disposition of: 4,844,548

(iv) Shared power to dispose or to direct the disposition of: —0—

Item 5. Ownership of Five Percent or Less of a Class

Yes. The Reporting Persons own 4.97% of the Issuer’s Common Stock outstanding.

Item 6. Ownership of More than Five Percent on Behalf of Another Person.

As the general partner of the Funds, Deer VI may be deemed to beneficially own all 6,890,120 Shares held directly by the Funds and have the power to direct the dividends from or the proceeds of the sale of such Shares.

Item 7. Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company.

Not applicable.

Item 8. Identification and Classification of Members of the Group.

Exhibit 1 sets forth information regarding the identity of members of a group. The Reporting Persons disclaim membership in a group and this report shall not be deemed an admission by any of the Reporting Persons that they are or may be members of a “group” for purposes of Rule 13d-5 or for any other purpose.

Item 9. Notice of Dissolution of Group.

Not applicable.

Item 10. Certification.

Not applicable.

CUSIP No. 60040N105 13G Page 9 of 11 Pages

SIGNATURE

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

Date: February 13, 2015

DEER VI & CO. LLC
By:	/s/ J. Edmund Colloton
	Name: J. Edmund Colloton
	Title: Executive Manager
BESSEMER VENTURE PARTNERS CO-INVESTMENT L.P.
By: Deer VI & Co. LLC, General Partner
	By:	/s/ J. Edmund Colloton
		Name: J. Edmund Colloton
		Title: Executive Manager
BESSEMER VENTURE PARTNERS VI INSTITUTIONAL L.P.
By: Deer VI & Co. LLC, General Partner
	By:	/s/ J. Edmund Colloton
		Name: J. Edmund Colloton
		Title: Executive Manager
BESSEMER VENTURE PARTNERS VI L.P.
By: Deer VI & Co. LLC, General Partner
	By:	/s/ J. Edmund Colloton
		Name: J. Edmund Colloton
		Title: Executive Manager

CUSIP No. 60040N105 13G Page 10 of 11 Pages

EXHIBIT INDEX

Exhibit 1. List of Members of Group