Richard Dreyfuss as Roy Neary

François Truffaut as Claude Lacombe

Teri Garr as Ronnie Neary

Melinda Dillon as Jillian Guiler

Bob Balaban as David Laughlin

J. Patrick McNamara as Project Leader

Warren J. Kemmerling as Wild Bill

Roberts Blossom as Farmer

Phil Dodds as ARP Musician

Cary Guffey as Barry Guiler

Shawn Bishop as Brad Neary

Adrienne Campbell as Sylvia Neary

Justin Dreyfuss as Toby Neary

Lance Henriksen as Robert

Merrill Connally as Team Leader

Amy Douglass as Implantee

Gene Dynarski as Ike

Carl Weathers as Military Policeman

Norman Bartold as Norman Bartold

F.J. O'Neil as ARP Project Member

Hal Barwood as Returnee #2 Flt. 19

Matthew Robbins as Returnee #3 Flt. 19

Gene Rader as Hawker

Daniel Nunez as Federale

Chuy Franco as Federale

Luis Contreras as Federale

Galen Thompson as Special Forces

John Dennis Johnston as Special Forces

Robert Broyles as Dirty Tricks #3

George DiCenzo as Major Benchley

Alexander Lockwood as Implantee

Josef Sommer as Larry Butler

Bill Thurman as Air Traffic

James Keane as Radio Telescope Team

Philip Dodds as Jean Claude

Mary Gafrey as Mrs. Harris

Michael J. Dyer as Himself

Roger Ernest as Highway Patrolman

Randy Hermann as Returnee #1 Flt. 19

David Anderson as Air Traffic Controller

Richard L. Hawkins as Air Traffic Controller

Craig Shreeve as Air Traffic

Roy E. Richards as Air East Pilot

Eumenio Blanco as Federale

Dennis McMullen as Radio Telescope Team

Cy Young as Radio Telescope Team

Tom Howard as Radio Telescope Team

Richard Stuart as Truck Dispatcher

Bob Westmoreland as Load Dispatcher

Matt Emery as Support Leader

John Ewing as Dirty Tricks #1

Kirk Raymond as Dirty Tricks #4

Keith Atkinson as Dirty Tricks #2

Monty Jordan as Special Forces Commander / Helicopter Pilot (uncredited)

Basil Hoffman as Longly (uncredited)

Stephen Powers as UN Observer (uncredited)

J. Allen Hynek as Man Smoking Pipe at Landing Site (uncredited)

Howard K. Smith as Howard K. Smith (uncredited)