Shia LaBeouf as Sam Witwicky:
An offbeat seventeen-year old, Sam gets his first car, which turns out to be Bumblebee. Sam unwittingly becomes the center of the Autobot-Decepticon war, and becomes the unlikely savior of humanity.
Megan Fox as Mikaela Banes: A girl whom Sam is interested in and woos with the help of Bumblebee. Her father was a "grease monkey" and she has inherited some of his skills.
Josh Duhamel as Cpt William Lennox: Leader of a U.S. Army Special Ops US Ranger team in Qatar, who manages to escape the destruction caused by Blackout. He has a wife and new-born daughter back home.
Tyrese Gibson as TSgt Epps: An Air Force Combat Controller who teams up with Lennox to escape Blackout and Scorponok.
John Turturro as Simmons: An officer in Sector 7, a secret government group that has been holding and studying the Allspark and the frozen Megatron. Simmons is leading a team tracking down the Cybertronians.
Jon Voight as John Keller: The United States Secretary of Defense.
Rachael Taylor as Maggie Madsen: An expert in signal detection and decoding assisting the Department of Defense.
Anthony Anderson as Glenn Whitmann: A computer hacker and friend of Maggie, who assists in deciphering the Cybertronian language.
Bernie Mac as Bobby Bolivia: The car dealer who unknowingly sells Bumblebee (as an early model Camaro), to Sam.
Peter Cullen as the voice of Optimus Prime (Peterbilt truck): The wise and powerful Autobot leader who comes to protect humanity from the evil Decepticons. He wields a cannon and a blade.
Mark Ryan as the voice of Bumblebee (Second/Fifth generation Chevrolet Camaro): Bumblebee is an honest and friendly soldier who develops a friendship with Sam and Mikaela during his efforts to find the Allspark. He has difficulty speaking after his vocal processors were damaged in battle, and uses soundbites from radio broadcasts to communicate on Earth.
Darius McCrary as the voice of Jazz (Modified Pontiac Solstice): Optimus' second-in-command, he is a small but acrobatic fighter, with magnetic hands. He develops a fondness for human culture.
Jess Harnell as the voice of Ironhide (GMC Topkick 6500 pick-up truck): The tough, trigger-happy weapons specialist of the group, wielding enormous cannons on his arms. He is an old friend of Optimus, and constantly threatens to use deadly force on terrestrial life forms, much to Optimus's dismay.
Robert Foxworth as the voice of Ratchet (Search & Rescue Hummer H2): The team's medic and scientist. He has enhanced senses, and has an axe and a saw.
Hugo Weaving as the voice of Megatron (Cybertronian "jet"): The brutal Decepticon leader who desires power over the Allspark. According to Peter Cullen, Optimus and Megatron are brothers, akin to the story of Cain and Abel. He crash-landed in the Arctic eons ago, and his frozen body is kept in storage by Sector 7. He wields a flail and his arms form a cannon.
Charlie Adler as the voice of Starscream (F-22 Raptor): Megatron's second-in-command, who is berated for failing him repeatedly.
Jess Harnell as the voice of Barricade (Saleen-modified Ford Mustang police car): The Decepticon who locates Sam early on.
Reno Wilson as the voice of Frenzy (GPX 2-speaker CD player, mobile phone): The smallest Decepticon, Frenzy attaches to Barricade. His main purpose is spying on humans, but he is still a ferocious fighter, shooting blades disguised as CDs from his chest.
Jimmie Wood as the voice of Bonecrusher (Buffalo H Mine-Protected vehicle): He attacks Optimus Prime during the highway chase.
Blackout (MH-53 Pave Low III): He can fire electromagnetic pulses and wield his rotor blades as a weapon. He carries Scorponok.
Scorponok (mechanical scorpion): A minion of Blackout sent to hunt survivors of the attack on the U.S. military base in Qatar. Resembling a scorpion, he is armed with a razor tipped tail and plasma cannon claws, and burrows in and out of the sand.
Devastator (Modified M1A1 Abrams): He attacks the Autobots alongside Megatron and Starscream in the climactic battle. He is referred to as Brawl for the toyline.