Bumblebee crashes onto Earth and is tasked by Optimus Prime to find an object that will lead them to the missing AllSpark. He battles Decepticon drones and discovers that the Decepticons are after a family artifact belonging to Sam Witwicky. To protect Sam, Bumblebee heads to his home and later drives to a used car lot, where Sam buys him. Bumblebee then works to clear a path for the Autobots, defeating more Decepticon drones along the way, and helps them land safely.

As the story progresses, Sector Seven discovers the Autobots, and Bumblebee helps Sam and Mikaela escape. However, Jazz is caught by the humans, and Optimus Prime intervenes, engaging in a battle with the Decepticon Shockwave. Optimus learns from Shockwave's transmission that the Decepticons have found Megatron and the AllSpark at Hoover Dam. The Autobots head there to stop the Decepticons and retrieve the AllSpark, with Bumblebee narrowly escaping captivity and managing to shrink the AllSpark for transport.

At Hoover Dam, Bumblebee battles security systems to retrieve the AllSpark but is attacked by a thawing Megatron. He escapes with Sam, Mikaela, and the AllSpark, only for Starscream and Blackout to arrive, releasing Megatron. The Autobots then head to Mission City, where the AllSpark’s energy overloads, creating energon drones. Bumblebee loses control but is rescued by Ironhide. Starscream, Blackout, and Barricade are defeated in battle, but Megatron flicks Bumblebee aside and forces Sam and Mikaela to hide with the AllSpark.

In the final battle, Megatron confronts Sam and Mikaela but is stopped by Optimus Prime, who engages in a brutal fight with him. After a long struggle, Optimus defeats Megatron by thrusting the AllSpark into his chest, killing him. The Autobots reflect on the loss of the AllSpark but find a new purpose on Earth, with Optimus vowing to protect their new home.