UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, DC 20549

FORM 8-K

CURRENT REPORT PURSUANT

TO SECTION 13 OR 15(D) OF THE

SECURITIES EXCHANGE ACT OF 1934

Date of report (Date of earliest event reported) October 26, 2010

Affiliated Managers Group, Inc.

(Exact Name of Registrant as Specified in Its Charter)

Delaware

(State or Other Jurisdiction of Incorporation)

(617) 747-3300

(Registrant’s Telephone Number, Including Area Code)

N/A

(Former Name or Former Address, if Changed Since Last Report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2. below):

o    Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

o    Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

o    Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

o    Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

ITEM 2.02           Results of Operations and Financial Conditions.

On October 26, 2010, Affiliated Managers Group, Inc. (the “Company”) issued a press release setting forth its financial and operating results for the quarter ended September 30, 2010.  A copy of this press release is furnished as Exhibit 99.1 hereto and is hereby incorporated by reference herein.

ITEM 5.03                                 Amendments to Articles of Incorporation or Bylaws; Change in Fiscal Year.

The Board of Directors (the “Board”) of the Company approved an amendment to the Company’s Bylaws, effective October 26, 2010, which provides for the appointment of a lead director to the Board, and outlines the principal responsibilities of that position.

ITEM 8.01           Other Events.

The financial statement tables set forth in the press release issued by the Company on October 26, 2010 are also filed as Exhibit 99.2 hereto and are hereby incorporated by reference herein.

On October 26, 2010, the Company issued a press release announcing that, effective January 1, 2011, Sean M. Healey, President and Chief Executive Officer of the Company, will become Chairman of the Board, succeeding founder and Chairman William J. Nutt as Chairman.  Mr. Nutt will remain a member of the Board.  A copy of this press release is attached hereto as Exhibit 99.3 and is hereby incorporated by reference herein.

ITEM 9.01           Financial Statements and Exhibits.

(c)           Exhibits.

*  This exhibit shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, or otherwise subject to the liability of that section, nor shall it be incorporated by reference into any filing under the Securities Act of 1933 or the Securities Exchange Act of 1934.

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SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

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EXHIBIT INDEX

*  This exhibit shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, or otherwise subject to the liability of that section, nor shall it be incorporated by reference into any filing under the Securities Act of 1933 or the Securities Exchange Act of 1934.

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Exhibit 99.1

AMG Reports Financial and Operating Results

for the Third Quarter and Nine Months Ended September 30, 2010

Company Reports Economic EPS of $1.50; EPS of $0.65

BOSTON, October 26, 2010 — Affiliated Managers Group, Inc. (NYSE: AMG) today reported its financial and operating results for the third quarter and nine months ended September 30, 2010.

For the third quarter of 2010, Economic Earnings Per Share (“Economic EPS”) were $1.50, compared to $1.05 for the same period of 2009, while diluted earnings per share for the third quarter of 2010 were $0.65, compared to $0.40 for the same period of 2009.  For the third quarter of 2010, Economic Net Income was $77.9 million, compared to $45.6 million for the same period of 2009.  For the third quarter of 2010, Net Income was $34.0 million, compared to $17.8 million for the same period of 2009.  (Performance measures Economic Net Income and Economic EPS are defined in the attached tables.)

For the third quarter of 2010, revenue was $354.4 million, compared to $217.5 million for the same period of 2009.   For the third quarter of 2010, EBITDA was $102.3 million, compared to $60.5 million for the same period of 2009.

For the nine months ended September 30, 2010, Economic Net Income was $192.5 million, while EBITDA was $252.2 million. For the same period, Net Income was $76.6 million, on revenue of $937.5 million. For the nine months ended September 30, 2009, Economic Net Income was $125.8 million, while EBITDA was $162.9 million. For the same period, Net Income was $34.9 million, on revenue of $597.2 million.

Net client cash flows for the third quarter of 2010 were approximately $5.5 billion, with flows in the institutional, mutual fund, and high net worth channels of approximately $4.2 billion, $1.1 billion, and $0.2 billion, respectively.  The aggregate assets under management of AMG’s affiliated investment management firms were approximately $294 billion at September 30, 2010, pro forma for a pending investment.

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“AMG had an excellent quarter, reporting Economic Earnings Per Share of $1.50, an increase of 43% compared to the same quarter of last year,” stated Sean M. Healey, President and Chief Executive Officer of AMG.  “Our results reflect the successful execution of our growth strategy, including accretion from investments in new Affiliates as well as the strong organic growth of our existing Affiliates.  Our Affiliates continue to generate outstanding investment performance across an array of product areas, particularly in emerging markets and international equity and alternative products.  Given our industry-leading offerings in these product areas, we remain confident in our prospects for continued new business momentum as global institutional investors increasingly focus on expanding their allocations to alpha-generating strategies.”

“Over 70% of our EBITDA is now generated by global equity and alternative products, across a broad range of international markets and investment strategies, and our Affiliates participating in these areas delivered excellent results.  Global equity manager Tweedy, Browne and emerging markets manager Genesis continued to generate outperformance across all time periods in their flagship products, and Third Avenue’s Value fund ranked at the top of its Lipper category in the quarter.  In addition, Harding Loevner’s emerging markets equity product outperformed over both the near and long term, while alternative managers AQR, BlueMountain, and ValueAct realized substantial absolute returns across their largest products.  Finally, global private equity fund-of-funds manager Pantheon continued to perform well, with solid organic growth in the quarter.”

“With the continued outperformance of our Affiliates, AMG is well-positioned to benefit as investor risk appetite increases — particularly among clients outside the U.S., which already account for over half of our earnings,” Mr. Healey added.  “Our global distribution platform extends our boutique Affiliates’ marketing reach to large institutions in Australia, the Middle East, Europe, and now Asia.  As evidenced by our net client cash flows this quarter of $5.5 billion, we are seeing continued demand from sophisticated investors in these regions as AMG brings the outstanding performance of focused, return-oriented specialist firms, supported by the scale, resources, and risk management of a global investment manager, to strategic markets around the world.”

“We were pleased to announce our investment in premier global and emerging markets equity manager Trilogy Global Advisors during the quarter, which further enhanced our position in these product areas,” Mr. Healey concluded.  “We continue to see substantial opportunities for ongoing earnings growth through our New Investments strategy, with a strong and diverse pipeline of traditional and alternative firms, increasingly characterized by succession-driven transactions.  With our unparalleled competitive position and the favorable transaction environment, we are uniquely positioned to make additional accretive investments in the highest quality boutique firms globally.”

About Affiliated Managers Group

AMG is a global asset management company with equity investments in leading boutique investment management firms.  AMG’s innovative partnership approach allows each Affiliate’s management team to own significant equity in their firm while maintaining operational autonomy.  AMG’s strategy is to generate growth through the internal growth of existing Affiliates, as well as through investments in new Affiliates.  In addition, AMG provides centralized assistance to its

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Affiliates in strategic matters, marketing, distribution, product development and operations.  As of September 30, 2010, the aggregate assets under management of AMG’s Affiliates were approximately $294 billion, pro forma for a pending investment, in more than 350 investment products across a broad range of investment styles, asset classes and distribution channels.  For more information, please visit the Company’s website at www.amg.com.

Certain matters discussed in this press release may constitute forward-looking statements within the meaning of the federal securities laws.  Actual results and the timing of certain events could differ materially from those projected in or contemplated by the forward-looking statements due to a number of factors, including changes in the securities or financial markets or in general economic conditions, the availability of equity and debt financing, competition for acquisitions of interests in investment management firms, the ability to close pending investments, the investment performance of our Affiliates and their ability to effectively market their investment strategies, and other risks detailed from time to time in AMG’s filings with the Securities and Exchange Commission.  Reference is hereby made to the “Cautionary Statements” set forth in the Company’s Form 10-K for the year ended December 31, 2009.

AMG routinely posts information that may be significant for investors in the Investor Information section of its website, and encourages investors to consult that section regularly.  For additional information, please visit www.amg.com.

Financial Tables Follow

A teleconference will be held with AMG’s management at 11:00 a.m. Eastern time today.  Parties interested in listening to the teleconference should dial 1-877-407-9210 (domestic calls) or 1-201-689-8049 (international calls) starting at 10:45 a.m. Eastern time.  Those wishing to listen to the teleconference should dial the appropriate number at least ten minutes before the call begins.

The teleconference will also be available for replay beginning approximately one hour after the conclusion of the call.  To hear a replay of the call, please dial 1-877-660-6853 (domestic calls) or 1-201-612-7415 (international calls) and provide account number 286 and conference ID 357598.  The live call and replay of the session, and additional financial information referenced during the teleconference, can also be accessed via the Web at http://www.amg.com/InvestorRelations.

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Affiliated Managers Group, Inc.

Financial Highlights

(dollars in thousands, except per share data)

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Affiliated Managers Group, Inc.

Financial Highlights

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Affiliated Managers Group, Inc.

Reconciliations of Earnings Per Share Calculation

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Affiliated Managers Group, Inc.

Reconciliations of Average Shares Outstanding

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Affiliated Managers Group, Inc.

Operating Results

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Assets Under Management

Statement of Changes - Quarter to Date

Statement of Changes - Year to Date

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Affiliated Managers Group, Inc.

Operating Results

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Financial Results

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Affiliated Managers Group, Inc.

Reconciliations of Performance and Liquidity Measures

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Affiliated Managers Group, Inc.

Consolidated Statements of Income

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Affiliated Managers Group, Inc.

Consolidated Balance Sheets

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Affiliated Managers Group, Inc.

Consolidated Statements of Cash Flow

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