Super Mario Bros. 3 is a single-player and multiplayer side-scrolling platform game. The story follows Mario and Luigi as they travel through the Mushroom World after Bowser and his seven children, the Koopalings, steal magical wands from the kings of each realm. The Koopalings use the wands to transform the kings into animals, while Princess Peach is once again kidnapped and held hostage. The brothers must restore the kings to their true forms, reclaim the wands, and ultimately confront Bowser to rescue the princess.

Gameplay builds on the foundations of the earlier Super Mario Bros. titles but expands them significantly with larger levels, greater variety, and new mechanics. Players move across themed worlds, each composed of multiple stages connected by a world map. Navigation on the map allows the choice of paths, access to Toad Houses for bonus items, and encounters with wandering Hammer Bros. or other enemies. Levels feature the classic platforming formula of running, jumping, and stomping on enemies, combined with obstacles such as pipes, moving platforms, and environmental hazards.

Power-ups play a central role, combining returning items such as the Super Mushroom and Fire Flower with new additions that introduce more diverse abilities. The Super Leaf transforms Mario into Raccoon Mario, allowing him to attack with his tail and briefly fly after gaining running speed. Other suits include the Frog Suit for enhanced swimming, the Tanooki Suit for flying and temporary stone transformations, and the Hammer Suit, which allows throwing hammers similar to those of the Hammer Bros. The Starman returns, granting invincibility for a short period, while the rare Warp Whistle lets players skip ahead to later worlds.

Progression through the game requires clearing standard platform stages, fortress mini-castles guarded by Boom Boom, airship stages where the Koopalings are fought, and Bowser’s stronghold. Defeating a Koopaling recovers the stolen wand and restores a king to normal. In two-player mode, players alternate control between Mario and Luigi on the world map, with the opportunity to compete in bonus games inspired by the original Mario Bros. arcade title.

Each world in the Mushroom World has its own theme, such as grasslands, deserts, water stages, giant-sized enemies, icy landscapes, and even sky and pipe-based environments. These settings not only alter the appearance of stages but also introduce unique hazards and level designs, ensuring variety across the eight main worlds. The game also contains numerous secrets and hidden paths, encouraging exploration and experimentation.