Aliens: Infestation is a side-scrolling action/platformer that takes heavy inspiration from Nintendo's Metroid series and from latter-day Castlevania side-scrollers.

Infestation follows a group of Colonial Marines in a story placed just after the events of the film Aliens. Players control up to nineteen Marines as they explore now deadly locales such as the U.S.S. Sulaco, planet LV-426, and the derelict ship. Each of the nineteen Marines are written with their own dialog and personalities, but play the same. Players can expect to encounter the classic humanoid-inspired aliens, eggs, face-huggers, monstrous queens, and even chest-bursting babies. Besides the classic Xenomorphs of franchise fame, players will also face off against enemy soldiers and robots (or "synthetics" as they were known in the movies). A Colonial Marine Colonel is ever-present (by way of radio) to hand out orders and explanations of items in the game.

The game and map unfold in a manner highly reminiscent of Metroid games (perhaps ironic given the inspiration that franchise has taken from the Alien series) featuring large side-scrolling environments that gradually unfold as players explore the locations and gradually gain access to new areas. Like the aforementioned Metroid games, players will add to their armaments with a variety of weapons and tools, including the famous pulse rifles, flame-throwers, grenades, welding torches and others. Security access cards must be discovered to allow deeper access through areas in the game, and like the movies, the ventilation system is factored into movement and exploration.

While the game is an action-packed side-scroller, WayForward and Gearbox worked to transfer over the claustrophobic horror atmosphere of the original films. Players will encounter familiar sound effects through the game pulled straight from James Cameron's Aliens, and a tense horror atmosphere from Ridley Scott's original film. The survival horror aspect of the game receives an extra boost with the looming specter of permanent death. Players may find and use up to nineteen Colonial Marines to work through the game--but when they die, they're dead for good. Saving often, careful use of items, constant monitoring of the map screens, and the ever-present and familiar tick and hum of the classic (as in Aliens) motion sensor are intended to work together to keep players on edge through the game.

The game is played like a typical side-scroller or action-heavy platformer, and all action takes place on the top screen of the DS. The bottom screen is used for item inventory, weapon and item selection (or management), stats, and character selection. All in-game controls are performed with the D-pad and buttons, which allow players to shoot in all directions, either moving or stationary, along with running and dodge moves. Players may also hide up against boxes for safety during some situations. When the map screen is active (in place of the weapons and items interface), the familiar pulse of the motion sensor beeps and illuminates "lifeforms" as dots on the map. Map data must be discovered in an area before a map is useful on the bottom screen, however, unlike the typical Metroid game, some of the maps are not connected with one another and are, in fact, separate locations.