Lethal Weapon is a side-scroller, in which the player chooses one of the police partners (Mel Gibson or Danny Glover) and battles it out with criminals around the city and surrounding area. Battles are resolved via fists, guns and grenades. It is considered by many to be extremely difficult and frustrating in the fact that punching an enemy is more effective than shooting an enemy. It has minimal music and sparse interesting scenery.

There was another version of the game released for the day's home computer formats and the Super NES. It also is a difficult side-scroller where the user plays as either Riggs or Murtaugh and has to complete four missions in order to go on to the fifth and final mission. There is little difference between the two characters, other than Riggs having a faster rate of fire for his handgun, but at the cost of having a low jump height, while Murtaugh has a higher jump height at the cost of a low rate of fire for his handgun. The first four missions have the player trying to do things such as rescue Leo Getz, defuse a bomb in a shopping mall, stop a dockside smuggling operation, and prevent terrorists from blowing up the city's sewer system. The final mission focuses on going after Jack Travis, the main villain of Lethal Weapon 3.