UFO: Aftermath – a military strategy game about the war between humanity and alien invaders. According to the plot, in 2004, the Earth was visited by a spaceship, which destroyed most of the living creatures with spores. The few survivors either mutated into terrible monsters or were forced to hide and fight for life every day. The player's character is a representative of the Earth Council, which led the surviving people, and the commander of a combat unit. His main goal is to find out why the aliens destroyed civilization and whether it can be fixed.

An important element of the gameplay in UFO: Aftermath are bases. Unlike other strategies, they cannot be built here – they can only be remade from captured alien outposts or old earthling buildings. Bases allow you to send helicopters with combat squads, speed up the study of technologies and the creation of food. The gamer cannot personally control the squad – the results of the mission are determined automatically, depending on such factors as the type of task, human and alien ships.

Locations where you can complete the task are marked on the map. The gamer will be able to carry out such operations as clearing the territory of monsters, destroying the marked object or capturing a building from which you can make a base. Most missions are accompanied by a timer – if the gamer does not make it in time, the quest will be interrupted. According to the plot, the territory will be cleared by other soldiers, and the degree of success depends on how much the player managed to do.