Fallout: Brotherhood of Steel 2 was the canceled sequel to Fallout: Brotherhood of Steel and was in development by Interplay Entertainment who would self-publish it if it were ever made. The development of the game started before the completion of the original and its development caused the cancellation of Black Isle Studio’s Fallout 3. Like Fallout 3, the game was near completion when it was canceled. Like its predecessor, the game would have used the Dark Alliance Engine. It was targeted for a Christmas 2004 release date.

Like other Fallout games, the game would have used a reputation system, only simpler. The game would have featured fourteen new weapons and ten new enemies. Depending on whether the player is good or evil, the game would have played out differently. Each of the four characters that were playable would have had a different fighting style, therefore each time the player played the game, they would have a different experience. It would have had two player co-op action for players to experience the game with their friends. The Dark Alliance Engine would have been fleshed out and player experience would have been refined. A brand new sneak system would have been added to the game. This system would have allowed players to stealthily follow enemies or use a sniper rifle on them. For characters that could not use the sniper rifle, Interplay added a turret mode allowing those characters to use turrets.