In yet another sequel to the surprise family hit 3 Ninjas, the three young Ninja brothers, Rocky (Michael Treanor), Colt (Max Elliott Slade), and Tum Tum (Chad Power), are spending the summer with their grandfather (Victor Wong), who is tutoring them in the martial arts.
However, there are foul doings afoot -- Jack (Charles Napier), an unscrupulous business tycoon, has been dumping toxic waste on a nearby Indian burial ground and keeping the matter quiet with kickbacks to the local police.
When the Ninja brothers try to come to the aid of the local Indian tribe, Jack tries to intimidate them and their Native American friends, a plan that only makes the boys more determined to see that justice is done. 3 Ninjas Knuckle Up was actually shot in 1994, a year before 3 Ninjas Kick Back, and features the same three actors who played the Ninja brothers in the first film.
However, 3 Ninja Kick Back, which replaced two members of the original cast, was released first.