Injustice: Gods Among Us is a fighting game in which players control characters with different fighting styles and special attacks, engaging in one-on-one combat to deplete their opponent's life gauge. The game is in 2.5D:movement is restricted to a two-dimensional plane, while the characters and backgrounds are rendered in three-dimensions. Unlike the traditional fighting game design involving multiple rounds with regenerative life bars, Injustice uses a scheme similar to the Killer Instinct series. Each match consists of a single round with each player bearing two life bars. The game utilizes a four-button control layout of light, medium, and heavy attacks, alongside a "character trait" button, which activates a unique ability or attack designed to showcase each character. For instance, Superman's character trait provides a temporary boost in strength, while Batman's character trait summons a swarm of robotic bats.

The stages, based on various locations from the DC Universe, such as the Batcave, Metropolis, and the Fortress of Solitude, feature interactive environments and multiple areas. If an opponent is hit with a heavy attack near a corner of the arena, it launches them, triggering a transition animation and taking the fight to a new section of the stage. Each section also contains objects that characters can interact with differently depending on their class. Characters fall into two classes: "power characters", who rely on brute strength and innate abilities, and "gadget characters", who use weapons, items, and other external mechanisms to win. For example, a gadget character like Batman can attach a bomb to a car to cause an explosion, while a power character like Superman will pick up the same car and smash his opponents with it. Players have the option to turn off interactive elements and stage transitions.

As characters perform special moves, block oncoming attacks, or get hit by the opponent, their "super meters" will gradually fill. Portions of the super meter can be used to execute enhanced special moves or counter enemy moves. With a full meter, players can unleash their strongest special attack. Players may also expend their meter to interrupt a combo and enter a wager battle, dubbed the "clash system", which combines individualized cutscene cinematics with the process of betting meter. A clash may be triggered by a player only after they have lost their first life bar. During the sequence, both players commit portions of their meter in secret, with the highest bidder winning the clash.

The story mode is split into several chapters. As the narrative plays out, the player swaps between different characters. Minigames are also incorporated into the story. The outcome of minigames can impact an upcoming battle, such as giving the player a health advantage over the CPU opponent. Additional game features include Battle Mode, Versus Mode, Training Mode, and S.T.A.R. Labs, which includes 240 character-specific challenges of varying difficulty. Online multiplayer modes include King of the Hill, a setup that allows up to eight players to spectate a match while waiting for their turn to fight, and Survivor, which carries over the current winner's health bar and character selection over each match. Playing through any of the game modes, including online matches with optional goal objectives, will net the player experience points that may be used to unlock alternate costumes, music, concept art, and other rewards.

1. 40 S.T.A.R. Labs Missions