| Brian D. Lesser | |
| Birth Date: | c. |
| Education: | BA Political Science from the University of Pennsylvania, MBA from Columbia Business School |
| Occupation: | Businessman |
| Known For: | CEO of GroupM |
| Father: | Michael S. "Mike" Lesser |
| Children: | 3 |
Brian D. Lesser is an American businessman who is the former CEO of Xandr and the CEO of GroupM, a WPP company.
Born about 1975,[1] Lesser was introduced to the advertising industry at an early age by his father, Michael S. "Mike" Lesser, who was chairman and CEO of Lowe Marschalk (later Lowe & Partners Inc.),[2] then president of Ogilvy & Mather New York.[3] [4] [5] Mike Lesser was also general manager of The November Group, the advertising arm of the Committee for the Re-Election of the President Richard Nixon, known in pop culture as C.R.E.E.P formed solely to create an ad campaign for the 1972 United States presidential election.[6]
Brian Lesser received a BA in Political Science from the University of Pennsylvania in 1996, then earned an MBA from Columbia Business School in 2004. He resides in New Jersey with his wife and three children.[7]
In 2006, Lesser was vice president of 24/7 Media, then senior vice president of the Media Innovation Group, LLC (known as “The MIG”).
In 2011, he founded Xaxis as a subsidiary of GroupM; he then became CEO of GroupM in November 2015,[8] overseeing six media agencies.[9] As CEO from 2015-2017, WPP's business experienced a 2.3% decline on like-for-like business [10], while the broader advertising market grew by approximately 3.4% in 2017, indicating that GroupM underperformed relative to the industry.
In October 2017, Lesser was recruited by former GroupM client AT&T[10] as CEO of Advertising and Analytics.
In September 2018, Advertising and Analytics was renamed Xandr, a subsidiary of AT&T, and Lesser was appointed CEO.[11] Lesser resigned in 2020 after being informed he would not be appointed CEO of WarnerMedia, a position he had been considered for.[12] [13] [14]
During Lesser's tenure at AT&T's Xandr, InfoSum, a data clean room company, pitched and secured strategic investment from Xandr as part of its $15.1M Series A funding round which closed in September of 2020.
Three months later, in December 2020, Lesser stepped into the role of CEO and Chairman of InfoSum[15] which then raised another $65M in 2021. Though the firm's revenue, as of April 2025 was approximately $14.2M,[16] AdAge reported its 2021 valuation at $300M.
Lesser resigned as CEO and Chairman at InfoSum in July 2024 to become Global CEO at GroupM in September 2024. In 2025, it was announced that GroupM acquired InfoSum for $150M, and would then sit within GroupM, now led by Lesser.
In 2014, Lesser was named to the Ad Age's “40 Under 40” list[1] and, in 2018, was recognized by AdWeek as "Executive of the Year".[17]
