Deng has recovered sufficiently from a left wrist injury to be included in the 12-man squad announced Thursday.
Deng says the players "plan to make Britain proud" and adds that he can't "wait to step on the court with my teammates at the games."
Gordon and Mullens were already out of contention for Britain's first Olympic basketball team since 1948. The London-born guard Gordon didn't commit to playing at the games and Mullens is injured.
Another London-born player, forward Pops Mensah-Bonsu of the Turkish club Besiktas, also has been included in the squad.