Matt Damon as Will Hunting

Robin Williams as Sean Maguire

Ben Affleck as Chuckie Sullivan

Stellan Skarsgård as Gerald Lambeau

Minnie Driver as Skylar

Casey Affleck as Morgan O'Mally

Cole Hauser as Billy McBride

Vik Sahay as MIT Student

John Mighton as Tom

Rachel Majorowski as Krystyn

Colleen McCauley as Cathy

Matt Mercier as Barbershop Quartet #1

Ralph St. George as Barbershop Quartet #2

Rob Lynds as Barbershop Quartet #3

Dan Washington as Barbershop Quartet #4

Alison Folland as MIT Student

Derrick Bridgeman as MIT Student

Shannon Egleson as Girl on Street

Rob Lyons as Carmine Scarpaglia

Steven Kozlowski as Carmine Friend #1

Jennifer Deathe as Lydia

Scott William Winters as Clark

Philip Williams as Head Custodian

Patrick O'Donnell as Assistant Custodian

Kevin Rushton as Courtroom Guard

Jimmy Flynn as Judge Malone

Joe Cannon as Prosecutor

Ann Matacunas as Court Officer

George Plimpton as Psychologist

Francesco Clemente as Hypnotist

Jessica Morton as Bunker Hill Student

Barna Moricz as Bunker Hill Student

Libby Geller as Toy Store Cashier

Chas Lawther as MIT Professor

Richard Fitzpatrick as Timmy

Frank Nakashima as Executive #1

Chris Britton as Executive #2

David Eisner as Executive #3

Bruce Hunter as NSA Agent

Robert Talvano as NSA Agent #2

James Allodi as Security Guard

Michael Arthur as Reunion Guest (uncredited)

Christian Harmony as Student (uncredited)

Riva Di Paola as MIT Student (uncredited)

Harmony Korine as Hervé (uncredited)

Thomas Lundy as Waiter (uncredited)

Paul McGillicuddy as Race Track Fan (uncredited)

Daniel Olsen as MIT Student (uncredited)

Stephen L'Heureux as Bartender (uncredited)