Paper Mario: Sticker Star features a visual style similar to its predecessors, in which the characters appear as paper cutouts in a three-dimensional papercraft Mushroom Kingdom, with landscapes ranging from snowy areas and forests to volcanoes. The story focuses on Mario's efforts to retrieve the six Royal Stickers that have been scattered by Bowser at the annual Sticker Fest. Mario is accompanied by Kersti, a sticker fairy, who bestows upon Mario the power of stickers.
The player controls Mario as he explores the various locales of the Mushroom Kingdom. A major facet of Sticker Star's gameplay is the extensive use of collectible stickers, which are used to gain new abilities and progress through the game. The player collects stickers that are found and peeled off from various areas in the environment. The player can also purchase stickers using coins or receive them from non-playable characters. The player has limited inventory space, and larger stickers take up more room. Stickers are used both in combat and for interacting with the environment. The player can enter a state called "Paperization" that allows him to place stickers anywhere on the visible overworld to activate certain events. The player can also find real-world objects, such as baseball bats and scissors, that can be turned into special types of stickers, called "Thing Stickers", which are often needed to solve puzzles in the overworld. For example, a Fan Thing Sticker can be placed in strategic areas in the environment and, when activated, creates wind that moves or destroys obstacles.
The turn-based battles in Sticker Star are similar to those in the original Paper Mario and its first sequel, initiated when Mario comes into contact with enemies in the overworld. The player's available attacks are determined by the stickers currently on hand. For example, possession of the Jump sticker is required for Mario to attack an enemy by jumping on it. Thing Stickers are used to inflict more damage on enemies, and certain types of Thing Stickers are required to defeat boss characters. However, each sticker is removed from play after one use; it is necessary for the player to consistently collect new stickers. Unlike the previous titles, the player increases his maximum HP and other stats through collection of stickers instead of gaining experience awarded from winning battles. Bonuses or special events that occur during battles can increase Mario's attack power or allow him to use a single sticker multiple times.