Yet again Sonic & All-Stars Racing Transformed finds Sonic and friends caught up in Dr. Robotnik's schemes to exploit the power of Chaos, a malevolent being that feeds upon the power of the Chaos Emeralds. In their own way, five heroes will do what they can to save Station Square and perhaps the entire world.
The player can select from which character to play after meeting them with Sonic, and each has its own unique version of each level. Sonic 's levels involve racing through a level as quickly as possible, destroying any robots along the way. Tails' levels are similar, but he must beat an opponent to the finish line. Amy's levels focus on avoiding capture by robots sent after her, using her giant hammer to break obstacles. E102 Gamma is a slow robot with guns and missiles that can lock on to targets, while Big's levels are largely about fishing.
The game also features the ability to visit the Chao garden, where players can raise baby Chaos and grow stronger by petting, feeding, and showing animals found in levels to it. Each level has additional objectives that can be completed to acquire extra emblems, which do not affect gameplay. The game also had online capabilities for downloading additional levels and bonuses, but this feature is no longer available since SegaNet shut down.