Freeway Mutant is an arcade game where the player controls a green mutant, running down a dilapidated post-apocalyptic freeway. The mutant runs non-stop and can be moved left or right. In the player's way are holes, landmines, and monsters; contact with them means an immediate game over. The game keeps tab of the highest distance reached by the player.

The monsters can be destroyed with the mutant's gun, which he shoots automatically whenever there's a monster ahead of him. The gun can be upgraded between games by spending resources gathered along the freeway, including monster kidneys that fall out of killed enemies.