One or two players can take the role of a pair of United States Colonial Marines in an altered version of the film's storyline. The action begins with an escape from the spaceship Sulaco before proceeding to the surface of Fiorina 'Fury' 161, where players must take down hordes of Aliens as well as an army of Weyland-Yutani Corporation troops sent to retrieve specimens by any means necessary. Levels are based on sets from the film and take players through the Mess Hall, Infirmary, Lead Works and more. The game ends when the players defeat the unidentified man, only to be met with more troops.
The game was well received by video game critics. Retrospectively, Stephen Kleckner of GamesBeat wrote positively about Alien 3: The Gun, including it in his "must-play" list of Alien titles and opining it is better than 2006's light gun game Aliens: Extermination. According to Retro Gamer, the "terryfying and glorious" Alien 3 "went leagues beyond the other shoot-'em ups, such as Lethal Enforcers." Jon Thompson of All Game Guide gave it four stars out of five, calling it an "exciting" shooter "that does the movies proud, creating a horror-filled, action-packed atmosphere that should impress both die-hard and casual fans."