While working underground to fix a water main, Brooklyn plumbers Mario and brother Luigi are transported down a mysterious pipe and wander into a magical new world. But when the brothers are separated, Mario embarks on an epic quest to find Luigi.

With the assistance of a Mushroom Kingdom resident Toad (Keegan-Michael Key; The Lion King) and some training from the strong-willed ruler of the Mushroom Kingdom, Princess Peach, Mario taps into his own power.