B
- Charles L. Bartlett (journalist), 1956 winner of the Pulitzer Prize for National Reporting
- Mike Birbiglia, comedian (left), class of 1996
- Walter Van Rensselaer Berry, lawyer, friend and mentor of Edith Wharton
- Ben Bradlee, former editor, The Washington Post
- Nicholas F. Brady, U.S. Treasury Secretary (1988-93); New Jersey Senator (1982)
- Nicholas Braun, actor
- Doug Brown, former National Hockey League player
- Greg Brown, former National Hockey League player
- Edward Burnett, U.S. representative from Massachusetts
Read more about this topic: List Of St. Mark's School (Massachusetts) Alumni