Imperium Romanum: Emperor Expansion is an add-on for Imperium Romanum. It features four new campaigns with overall 19 unrelated missions. It also brings two new features on the table: Now the player can associate a god with his city which gives certain bonuses, e.g. extinguishing fires faster, and optionally play with randomly assigned tasks instead of fixed ones. To motivate the player even further this expansion also adds an achievement system.

The game also includes the DLCs Imperium Romanum: The Conquest of Britannia and Imperium Romanum: Wilds of Germania.