Postal 3 is a third-person shooter about the Dude who moves to Catharsis, a city located near his hometown. The gameplay is designed on the Source engine, unlike the previous part, created on the Unreal Engine. The walkthrough begins with the main character accidentally blowing up the town of Paradise after a bad first day at the office.

After the explosion, along with his dog friend, the Dude finds himself in Catharsis. This place is slightly better than Paradise, but even here you can meet with psychotic extremists, a corrupt and hypocritical government, which is why the life of the population is very similar. On the path of the central character, law enforcement agencies, natural fanatics, gay bikers and aggressive local animals will again come across. As in other parts of the franchise, the gameplay of Postal III is endowed with surrealism, aimed at a fun narrative with elements of dark and unethical humor.

The plot is linear, the gamer receives basic tasks to complete. In the second part, the user had freedom of action and the opportunity to travel through open locations. Here you have to follow corridor territories. Shooting off limbs or hitting an enemy in the head will instantly kill him. There are 2 original styles of passing: Good and Evil. The karma meter has two opposite statuses. The scale is affected by good and bad deeds as you progress. By arresting or paralyzing opponents, negative karma is reduced. If you kill enemies, the positive karma scale worsens.