The game is played from a first-person point of view and scrolls horizontally in two directions as various enemy creatures, possessed soldiers, human vehicles and alien vehicles attack the player character. Alien Brigade can either be played with the Atari 7800 joystick or with an Atari light gun.
The game has five levels and four difficulty modes.The initial mission is to rescue hostages from an enemy camp, but the game then progresses to a waterfront battle, an underwater melee, a showdown in an underground mine, and then a final mountaintop battle. Adding to the challenge, the player must be careful not to shoot innocent bystanders.
Between levels, the player is briefed by the commanding officer, who advises of the situation and rates the player’s performance in the level.