Mortal Kombat 1 features a story mode, online multiplayer with rollback netcode, and offline gameplay, as well as cross-play and cross-progression, a first in the series.  The game introduces a feature called Kameo Fighters, who provide assistance to the player during fights in a similar fashion to the tag assist fighters of the Towers of Time mode in Mortal Kombat 11 (2019). These characters are separate from the main roster and are chosen before each fight. There are two types of assists provided by each Kameo Fighter: Summons, which can be performed while the player remains in one place, and Ambushes, which can be performed regardless of what the player is doing. They can also be called in to perform their own Fatalities and Brutalities. In addition, the chosen Kameo Fighter also affects how much health the players will have in a fight.