The maximum number of Impostors in one Among Us round is 3.
Among Us supports up to three Impostors in a standard round, with the exact number determined by the lobby's settings and player count. In a full multiplayer lobby, the host can configure the game so that three players are secretly assigned the Impostor role while the rest become Crewmates.
That maximum is not the same as the maximum number of players. Modern Among Us lobbies can hold up to 15 players, but a 15-player game still cannot have more than three standard Impostors. Smaller lobbies generally offer fewer Impostors to preserve the game's balance and deduction mechanics.
The role is hidden at the start of the round. Impostors can eliminate Crewmates, sabotage systems, and use vents, while Crewmates complete tasks and discuss suspicious behavior. Hide and Seek is a notable exception: it uses a single known seeker rather than the standard hidden-Impostor setup.