Like its parent, the Xbox Live Arcade game Geometry Wars: Retro Evolved, Galaxies has the player control a ship that can shoot and travel in 8 directions and is controlled primarily with analog sticks and a single button to activate bombs. The playing space is a flat 2D plane, but unlike Evolved there are multiple planes (or levels) that vary in size and shape. The planes are typically a near-black background lit up with a grid, but enemies are brightly colored shapes that fill the screen with particles and colors when attacking the player.

Galaxies differs from Retro Evolved in that the single-player component has many different levels rather than the single provided in Evolved, each with its own set of score goals. Galaxies also adds a new mechanic of the drone, which acts as a helper ship that can perform one user-selected duty at a time such as rotating shield, secondary shooter, backwards shooter, etc.

The Wii version includes Geometry Wars: Retro Evolved and can interface with the Nintendo DS to download the demo to the system, as well as to unlock new features, including a hidden version of Geometry Wars: Waves.