Although tower defence may be classified under the umbrella of RTS, its gameplay mechanics have evolved such that they are significantly distinguishable. Many tower defence games employ a rail path for enemies to follow (bloons, plants vs zombies), rather than the RTS approach of an open field. This increases the level of strategy required when placing towers, placement of which may also be pre-allocated. Games like Sanctum allow for free placement of turrets and derailed mobs, allowing for on-the-fly path construction and alteration, as well as adding an FPS element.

Tower defence games offer a more Arcade-level style of gameplay in comparison to their older relative, the RTS, with smaller levels and less freedom, but with fast paced and intense gameplay. Examples include Revenge of the Titans, Anomaly 2 and Dungeon Defenders.