After the events of the previous film, the Mario brothers finally continued their Brooklyn careers as plumbers, only to find their rivals such as the Wario Bros. trying to foil their jobs, which Mario & Luigi successfully outsmarted them.
However, the Mario brothers return to the Mushroom Kingdom to join Princess Peach, Toad, Donkey Kong & Yoshi in an all-round adventure to save the world from the evil clutches of Bowser, along with his son Bowser Jr, the Koopa army, and new enemies such as the Koopalings & the Wario Bros.