Mercenary Kings is a 2D arcade run-and-gun game with graphics similar to Scott Pilgrim vs. The World: The Game. The gameplay is somewhat similar to the Metal Slug series, but levels are less linear in design. The player chooses one from two mercenaries (male King and female Empress characters). In the main base he can talk with various characters, buy stuff and take on missions from the general.

During missions the character must fight hordes of enemies and complete tasks. Goals are mainly destroying structures, retrieving items, rescuing people and killing enemies. The character has two main weapons: a gun and a knife. The gun needs to be reloaded regularly. The game has cooperative multiplayer, both offline and online.