Super Mario Bros. 2 is a 2D side-scrolling platform game. The objective of the game is to navigate the player's character through the dream world Subcon and defeat the main antagonist Wart.[4]: 3–4  Before each stage, the player chooses one of four different protagonists to use: Mario, Luigi, Toad, and Princess Toadstool. Unlike the previous game, this game does not have multiplayer functionality. There is also no time limit to complete any level. All four characters can run, jump, and climb ladders or vines, but each character possesses a unique strength that causes them to be controlled differently. For example, Luigi can jump the highest; Princess Toadstool can float; Toad's strength allows him to pick up items quickly; and Mario represents the best balance between jumping and strength. As opposed to the original Super Mario Bros., which only moved from left to right, players can move either left or right, as well as vertically in waterfall, cloud and cave levels. Unlike other Mario games, the characters cannot defeat enemies by jumping on them; but they can stand on, ride on, and jump on the enemies. Instead, the character picks up and throws objects at the enemies or throws the enemies away to defeat them. These objects include vegetables dug from the ground or other enemies.[4]: 13–16 
The game consists of 20 different levels across the seven worlds comprising Subcon. Each world has three levels, except World 7, which has two.[4]: 6  Each world has a particular theme that dictates the obstacles and enemies encountered in its levels, such as desert areas with dangerous quicksand and snowy areas with slippery surfaces. Levels contain multiple sections or rooms that are connected via doors or ladders. Some rooms are accessible by entering certain jars. Magic potions found in each level are used to temporarily access "Sub-space", an inverted area where the player can collect coins and Mushrooms that increase the character's maximum health. In addition, certain jars, when entered in Sub-space, will warp the player to the later worlds, skipping levels altogether. Other items available include cherries, which are collected in order to acquire a Star; and the POW Block, which can be used to quickly destroy all the enemies visible on the screen.[4]: 17–21  The player must defeat a boss enemy at the end of each of the first six worlds, then defeat Wart himself at the end of World 7 to complete the game.
The player starts Super Mario Bros. 2 with three lives, which are lost each time the player's character loses all health from enemy or hazard damage or when the character falls off the screen. The player can replenish health by collecting floating hearts that appear upon defeating a certain number of enemies. The player will receive a Game Over upon losing the last life, though the player may continue up to twice in one game. Additional extra lives may be obtained by collecting hidden 1-Up Mushrooms or by using the coins collected from Sub-space to win the Bonus Chance minigame played between the levels.[4]: 9–10, 19, 22