James 'Whitey' Bulger
John Connolly
Marianne Connolly
Lindsey Cyr
FBI Agent Charles McGuire
Billy Bulger
Brian Halloran
Deborah Hussey
Kevin Weeks
John Morris
FBI Agent Robert Fitzpatrick
Fred Wyshak
John Callahan
Mickey Maloney
John McIntyre
Tommy King
DEA Agent Eric Olsen (Interrogator)
Mom Bulger
Mary Bulger
Douglas Cyr
Buddy Leonard
Jeremiah O'Sullivan
Joe Cahill
Mrs. Cody
Roger Wheeler
State Captain
Stephen Flemmi
Agent Scott Gariola
Josh Bond
McGuire's Secretary
Young Boy
Anna Bjornsdottir
Officer Flynn
Irish Nationalist
FBI Wire Tech
Joey, Big Italian
Gennaro Angiulo
Charlie McTiernan
Charlie's Friend
Agent James
Dick Lehr
Gerard O'Neill
Prisoner
FBI Agent
Father Mackey
Michael Donahue
DEA Agent
Nurse
Drug Dealer
Drug Dealer
Drug Dealer
Crook
Barman
Boot Shop Owner
World Jai Alai Chairman
Porthole Bartender
Porthole Customer
DEA Agent Dan Doherty
Little Mary Bulger
Kathleen Bulger
Driver
Charlie's Friend
Floor Dancer (uncredited)
Trevor Williams (uncredited)
Sr. FBI Official (voice)
John Martorano
The Mayor
Walker
Press Photographer
Marion Hussey (uncredited)