Keanu Reeves as Klaatu

Jennifer Connelly as Helen Benson

Jaden Smith as Jacob Benson

Jon Hamm as Michael Granier

Kathy Bates as Regina Jackson

John Cleese as Professor Barnhardt

Kyle Chandler as John Driscoll

Robert Knepper as Colonel

Brandon T. Jackson as Target Tech

James Hong as Mr. Wu

Jake McLaughlin as Soldier

John Rothman as Dr. Myron

Sunita Prasad as Rouhani

Juan Riedinger as William Kwan

Sam Gilroy as Tom

Tanya Champoux as Isabel

Rukiya Bernard as Student

Mousa Kraish as Yusef

J.C. MacKenzie as Grossman

Kurt Max Runte as Civil Engineer

Daniel Bacon as Winslow

Reese Alexander as Sergeant

Richard Keats as Helicopter Scientist #1

Bill Mondy as Helicopter Scientist #2

Judith Maxie as Helicopter Scientist #3

Serge Houde as Scientist #1

Lorena Gale as Scientist #2

Stefanie Samuels as Guardswoman

Richard Tillman as Army Sergeant

Camille Atebe as NYPD #1

Thomas Bradshaw as NYPD #2

Terence Dament as NYPD #3

Patrick Sabongui as Soldier #1

Jacob Blair as Soldier #2

Shaine Jones as Soldier #3

George Sharperson as Cop

Shaker Paleja as Medic #1

Doug Chapman as Medic #2

Marci T. House as Medic #3

Aaron Craven as Technician

Roger Cross as General Quinn

Heather Doerksen as Regina's Aide

Hiro Kanagawa as Dr. Ikegawa

Craig Stanghetta as Grey Man

Stefan Busse as Grey Man

Dean Redman as Military Policeman

David Richmond-Peck as Polygraph Operator

Andrew Wheeler as Guardsman

Darien Provost as Little Boy

Daniel St. Andrews as Train Passenger #1

Brad Dryborough as Train Passenger #2

Ken Kirzinger as Arguing Evacuee

William 'Big Sleeps' Stewart as Transit Cop

Blair Redford as Army Fighter Pilot #1

Daniel Wisler as Army Fighter Pilot #2

Mark Kogan as Air Traffic Controller

Ed Fong as Wu's Grandson

Sandy Colton as Army Corps Engineer Captain

Ty Olsson as Flash Chamber Colonel

Jay-Nicolas Hackleman as State Trooper

Dawn Chubai as News Anchor

Joshua Close as Flash Chamber Engineer

Leanne Adachi as Flash Chamber Tech

Geoff Meed as Field Commander Communications Officer

Michael Hogan as General

Ben Cotton as Truck Driver

Kevan Kase as Pickup Truck Driver

Josue Aguirre as Humvee Soldier

Matt Adler as (voice)