He previously served as the general manager of the New York Mets from 2011 to 2018, an executive in the Oakland Athletics and San Diego Padres organizations, and the commissioner's office of Major League Baseball.

Roy Eisenhardt, one of the firm's partners, left to become president of the Oakland Athletics when his father-in-law, Walter A. Haas Jr., bought the team.

In 1995, Haas died and the team's new owners, Stephen Schott and Ken Hofmann, ordered Alderson to slash payroll.

[5] Alderson served as chief executive officer for the San Diego Padres from 2005 to 2009, with the team winning back-to-back division titles in 2005 and 2006.

[6] Alderson was hired by the New York Mets after the 2010 baseball season to replace Omar Minaya as the general manager.

[7][8] Mets owner, Fred Wilpon, was dealing with his involvement in the Madoff investment scandal, and Alderson worked with a limited budget.

[12] From 2012 to 2014, Alderson reduced the Mets payroll to under $100 million, and exchanged veterans to acquire young talent such as Zack Wheeler, Noah Syndergaard, and Travis d'Arnaud.

Alderson also developed players drafted by Minaya such as Matt Harvey, Jacob deGrom, and Steven Matz.

In January 2019, Alderson returned to the Oakland Athletics as senior advisor of baseball operations to general manager Billy Beane.