Lego Dimensions features the same style of gameplay as the previous Lego video games developed by Traveller's Tales, in which up to two players control Lego minifigures based on various represented franchises. Players progress through linear levels, using their characters' abilities to solve puzzles, defeat enemies, and attempt to reach the level's end. Characters are entered into the game by placing their respective minifigures onto a USB toy pad, with each character possessing unique abilities that can be used to solve puzzles or reach hidden areas. Using a character from a certain franchise will also unlock that franchise's Adventure World, an open-world area for players to explore and complete in-game objectives.
The Starter Pack includes the toy pad and the game's 14-level main story campaign, which revolves around Batman, Gandalf, and Wyldstyle, while additional levels are made available by purchasing Level Packs and Story Packs. In addition to the minifigures, players can also build models of vehicles, such as the Batmobile, TARDIS, Mystery Machine, or DeLorean, and put them into the game for characters to drive. Completing objectives in the levels and adventure worlds will reward players with gold bricks, which can be used to upgrade vehicles and give them new abilities. Each adventure world also contains a red brick for players to retrieve; these will unlock special bonuses, such as visual modifiers for characters or extra assistance at finding collectible items. Unlike series such as Skylanders, Disney Infinity, and Amiibo, the minifigures, vehicles, and the USB toy pad are all made from real Lego pieces and can be freely built and customized.
All minifigures and vehicles can be used in any available level, though specific figures must be present to initially enter those levels or worlds. An additional feature called "Hire a Hero" was added shortly after the game's launch; this feature allows players to pay in-game currency to temporarily summon characters they do not own in order to complete an otherwise-inaccessible puzzle. The game's second year of content also introduced competitive multiplayer in the form of the Battle Arenas, allowing up to four players to compete in modes such as Capture the Flag. Gold bricks can be used to purchase new power-ups for the Battle Arenas. Certain packs also include exclusive features; for example, the Midway Arcade level pack unlocks playable emulations of over 20 Midway arcade titles, while the Teen Titans Go! packs unlock an exclusive Lego-themed episode of the series that can be viewed in-game.