Allen Greenberg is the executive director and president of the Susan Thompson Buffett Foundation, a charitable foundation established and funded by billionaire investor Warren Buffett. Greenberg was a left-of-center legal activist until his marriage to Buffett’s daughter Susie Buffett. As of 2025, they are divorced. ^{1 2}

Under Greenberg’s leadership, the Foundation grew into the third-largest private grantmaking foundation in America. Though the Foundation funds many causes, it is best known for championing population control and abortion access; as of 2014, the Foundation had provided more than $1.2 billion to organizations that perform and advocate for abortions. ³

Background and Family

Allen Greenberg was born in New York City in 1957. His father owned a newspaper-distribution company. Greenberg graduated from New York University Law School and began a career in left-of-center activist public-interest law. ⁴

In 1983, Greenberg met and married Susan Alice “Susie” Buffett, the oldest daughter of billionaire investor Warren Buffett. Warren and his first wife, Susan Thompson Buffett, favored Greenberg, reportedly referring to him as “Allen-the-perfect-son-in-law.” ⁵ Greenberg and Susan Alice met in Washington, D.C., but moved to Omaha, Nebraska in the late 1980s. ⁶ They divorced in 1995 ² and have two children together as of 2020. ⁶

Career

Early Career

Allen Greenberg started his career in law at Public Citizen, a left-wing advocacy organization founded by Green Party Presidential candidate and long-time left-of-center activist Ralph Nader. After working at Public Citizen, Greenberg took a job as a legal aide to then-U.S. Rep. Charles Schumer (D-NY). ⁴ After marrying Susie Buffett, Greenberg introduced Schumer to his father-in-law, Warren Buffett. ⁷

Susan Thompson Buffett Foundation

Reportedly upon Warren Buffet asking his daughter about her husband’s dream job, Greenberg was offered the executive director position at what was then called the Buffet Foundation in 1987. ⁶ Going back to its founding in 1964, the Foundation had never had an executive director before Greenberg,⁴ and for many years, he was the sole employee of the organization. ⁸

Even after Greenberg’s divorce from Susie Buffet in 1995, he has continued to lead the Foundation. ⁹ The Buffet Foundation was renamed the Susan Thompson Buffet Foundation in 2004 in honor of Warren Buffet’s late wife. ⁸

Warren Buffet has long expressed a desire to pass the vast majority of his accumulated wealth to charity upon his death, rather than allowing his children to inherit his estate in full. ¹⁰

According to colleagues and friends, Greenberg is a detail-oriented manager who personally oversees the Foundation’s outgoing grants. Inside Philanthropy notes that he “keeps a remarkably low profile,” particularly for an individual in charge of directing so many funds. ⁸ In 2023, Greenberg reported receiving over $800,000 in compensation for his role as executive director of the Susan Thompson Buffett Foundation.  ^{11 12}

As of 2024, Susie Buffett was the chair of the board of the Susan Thompson Buffett Foundation. According to Inside Philanthropy, she is the “driving force behind the foundation’s giving.”  ¹²

Inside Philanthropy named Allen Greenberg its “Foundation President of the Year” for 2019. The site noted Greenberg’s personal low profile, his efforts in making the Susan Thompson Buffett Foundation one of the biggest grantmakers in America, and his concerted efforts to block abortion restrictions across the US ¹³

1.  “Buffet Children Emerge as a Force in Charity.” The New York Times. Accessed January 5, 2020. https://www.nytimes.com/2006/07/02/business/02buffettkids.html
2. “Susan Alice Buffet.” Alchetron. Accessed January 5, 2020. https://alchetron.com/Susan-Alice-Buffett.
3. “Warren Buffett: The Billion-Dollar King of Abortion.” Media Research Center. Accessed January 6, 2020. https://www.mrc.org/articles/warren-buffett-billion-dollar-king-abortion.
4. “The Art of Giving when Your Resources are Vast.” Bloomberg. Accessed January 5, 2020. https://www.bloomberg.com/news/articles/1999-10-24/the-art-of-giving-when-your-resources-are-vast.
5. “Buffet: The Making of an American Capitalist,” by Roger Lowenstein. Random House Publishing. Read January 5, 2020. https://books.google.com/books?id=MFkKf4zIqbkC&pg=PA336&lpg=PA336&dq=allen+greenberg+public+interest&source=bl&ots=7CQG-K9xcp&sig=ACfU3U3ntK779lEJBKDkWKoypML_IcewCQ&hl=en&sa=X&ved=2ahUKEwidpfP-xevmAhWCq54KHQUnDg4Q6AEwCnoECAwQAQ#v=onepage&q=allen%20greenberg%20public%20interest&f=false
6. “Buffet Children Emerge as a Force in Charity.” The New York Times. Accessed January 5, 2020. https://www.nytimes.com/2006/07/02/business/02buffettkids.html.
7. “Chuck Schumer wants you to leverage his connections.” Politico. Accessed January 5, 2020. https://www.politico.com/states/new-york/albany/story/2016/02/chuck-schumer-wants-you-to-leverage-his-connections-030809.
8. “Who’s Who at the Secretive Susan Thompson Buffet Foundation?” InsidePhilanthropy.com. Accessed January 5, 2020. https://www.insidephilanthropy.com/home/2014/2/4/whos-who-at-the-secretive-susan-thompson-buffett-foundation.html.
9. “Return on Organization Exempt from Taxes (Form 990).” Susan Thompson Buffet Foundation. Accessed January 5, 2020. file:///C:/Users/Matt/Downloads/476032365_201812_990PF_2019080216539419.pdf.
10. “Billionaires Warren Buffett and Bill Gates have similar ideas about how much money you should leave your kids.” CNBC Make It. Accessed January 5, 2020. https://www.cnbc.com/2016/09/26/warren-buffett-bill-gates-have-similar-ideas-on-how-much-money-to-leave-kids.html.
11. “Susan Thompson Buffet Foundation,” Return of Private Foundation Exempt From Income Tax (Form 990 PF) 2023. Page 6 Part VII.
12. Callahan, David. “Who’s Who at the Secretive Susan Thompson Buffett Foundation?” Inside Philanthropy, February 4, 2014. https://www.insidephilanthropy.com/home/2014-2-4-whos-who-at-the-secretive-susan-thompson-buffett-foundation-html.
13. “Philanthropy Awards, 2019.” Inside Philanthropy. Accessed January 5, 2020. https://www.insidephilanthropy.com/home/2019/philanthropy-awards.