Johnny Depp
James 'Whitey' Bulger
Joel Edgerton
John Connolly
Julianne Nicholson
Marianne Connolly
Dakota Johnson
Lindsey Cyr
Kevin Bacon
FBI Agent Charles McGuire
Benedict Cumberbatch
Billy Bulger
Peter Sarsgaard
Brian Halloran
Juno Temple
Deborah Hussey
Adam Scott
FBI Agent Robert Fitzpatrick
Mark Mahoney
Mickey Maloney
Scott G. Anderson
Tommy King
Lonnie Farmer
DEA Agent Eric Olsen (Interrogator)
Erica McDermott
Mary Bulger
Lewis D. Wheeler
Jeremiah O'Sullivan
David De Beck
Roger Wheeler
Rory Cochrane
Stephen Flemmi
James Russo
Agent Scott Gariola
Danae Nason
McGuire's Secretary
Berglind Jonsdottir
Anna Bjornsdottir
David Conley
Officer Flynn
Ciaran Crawford
Irish Nationalist
Thomas Philip O'Neill
FBI Wire Tech
Joey Vacchio
Joey, Big Italian
Bill Haims
Gennaro Angiulo
Anthony Molinari
Charlie McTiernan
Declan Mulvey
Charlie's Friend
Richard Donelly
Gerard O'Neill
Patrick M. Walsh
Michael Donahue
Kathryn A. Beauchamp
Nurse
Stephen Curran
Drug Dealer
Darin X.L. MacEachern
Drug Dealer
Cary 'Big Shug' Guy
Drug Dealer
Jimmy Joe Maher
Boot Shop Owner
Forry Buckingham
World Jai Alai Chairman
Danny DeMiller
Porthole Bartender
Michael F. Murphy
Porthole Customer
Alexander Cook
DEA Agent Dan Doherty
Ava Cooper
Little Mary Bulger
Stella Cooper
Kathleen Bulger
Todd Ryan Jones
Charlie's Friend
Julie Ann Dawson
Floor Dancer (uncredited)
Fergaledgar
Trevor Williams (uncredited)
Robert E. Walsh
Sr. FBI Official (voice)
W. Earl Brown
John Martorano
Susan Garfield
Press Photographer
Colleen Kelly
Marion Hussey (uncredited)