Leonardo DiCaprio as Billy

Matt Damon as Colin

Jack Nicholson as Costello

Mark Wahlberg as Dignam

Martin Sheen as Queenan

Ray Winstone as Mr. French

Vera Farmiga as Madolyn

Anthony Anderson as Brown

Alec Baldwin as Ellerby

Kevin Corrigan as Cousin Sean

James Badge Dale as Barrigan

David O'Hara as Fitzy

Mark Rolston as Delahunt

Robert Wahlberg as Lazio (FBI)

Kristen Dalton as Gwen

Thomas B. Duffy as Govenor

Richard Hughes as Uncle Edward

J.C. MacKenzie as Realtor

Mary Klug as Billy's Aunt

Peg Holzemer as Mrs. Kennefick

Robert 'Toshi' Kar Yuen Chan as Triad Boss

Gurdeep Singh as Pakistani Proprietor

Armen Garo as Providence Gangster #1

John Cenatiempo as Providence Gangster #2

Joseph Riccobene as Kneecapped Bankrobber

Billy Smith as Detective #1 Tailing Queenan

Lyman Chen as Translator

Kevin P. McCarthy as Detective #1 - Colin's Unit

Chris Fischer as Detective #2 - Colin's Unit

Brian Smyj as Man Glassed in Bar

William Severs as Older Priest

Larry Mitchell as Younger Priest

Anthony Estrella as Police Camera Tech

Andrew Breving as Police Cell Phone Tech

Tracey Paleo as Darlene the Secretary

Douglas Crosby as Man Killed by French

Dorothy Lyman as Woman at Bar #1

Audrie Neenan as Woman at Bar #2

Frank Mallicoat as News Anchor

Paula DeMers as Billy's Mother

Conor Donovan as Young Colin

Amanda Lynch as Carmen

Sallie Toussaint as Woman at Opera

Patrick Coppola as Bookie Harassed by French

Mick O'Rourke as Jimmy Bags

Deborah Carlson as Sister Mary Theresa

Nellie Sciutto as Queenan's Secretary

Peter Welch as Other Prisoner

Henry Yuk as Chinese Government Man

Dennis Lynch as Costello's Crew #1

Michael Byron as Costello's Crew #2

William Lee as Costello's Crew #3

John Rue as Luncheonette Proprietor

Peter Crafts as Man in Costello's Bar

Joseph P. Reidy as Priest w/ Young Colin

John Farrer as Priest at Billy's Funeral

Paris Karounos as Jimmy Pappas

Brian Haley as Detective #2 Tailing Queenan

Terry Serpico as Detective #3 Tailing Queenan

Jay Giannone as Detective #4 Tailing Queenan

John Polce as Lynn Detective

Bo Cleary as Drill Instructor #2 (voice)

David Conley as Gang Member with Mr. French

Victor Chan as Chinese Delivery Man

Jill Brown as Executed Woman

Sarah Fearon as French's Wife

Denece Ryland as Woman Doctor

Daniel F. Risteen, Jr. as Crack House Cop #1

Francis P. Hughes as Crack House Cop #2

Johnny Cicco as Crack Addict

Chance Kelly as Exam Instructor

Shay Duffin as Bartender at Brasserie

John McConnell as Bookie in Costello's Bar

Kenneth Stoddard as State Trooper #1

Jeffrey Winter as State Trooper #2

Paddy Curran as New Guy

Mark Philip Patrick as New Guy

David Fischer as Executed Man

Walter Y.F. Wong as Waiter in Alley

Tony M. Yee as Waiter in Alley

Francesca Scorsese as Little Girl at Airport

Alex Morris as Young Man at Airport

Emma Tillinger Koskoff as Woman with Dog

Craig 'Radio Man' Castaldo as Crack House Denizen

Takumi Bando as Triad (uncredited)

Eric Bruno Borgman as Reporter (uncredited)

Brendan Burke as Irish Thug (uncredited)

Chris Chinn as Gang Member (uncredited)

Jeffrey Corazzini as Crime Scene Unit (uncredited)

Jim Ford as Cadet (uncredited)

Trudi Goodman as Woman Office Worker (uncredited)

Steve Lord as Academy Pistol Coach (uncredited)

Jack McCullough as EMT (uncredited)

Osmani Rodriguez as Reporter (uncredited)

Lawrence Cameron Steele as Academy Firearms Instructor (uncredited)

Conor Timmis as Rugby Fan (uncredited)

Joseph Oliveira as Officer (uncredited)

Adam Masnyk as Southie Teen / Soccer Player (uncredited)

John Franchi as Pedestrian (uncredited)

Paul McGillicuddy as Subway Passenger (uncredited)

Kim Carrell as MA State Police Detective

Rebecca Love as Adult Film Actress (uncredited)