Space Empires: Replicators, the second expansion in the Space Empires series, adds a number of features to the base game, starting with the Replicators. Von-Neumann Machines ("Replicators") are self-replicating machines that behave, research, and reproduce differently than other empires, while having their own Empire Advantages. Replicators can be used by a fifth player, as an opponent in co-op games, or as a teaching empire for new players as the Replicator player doesn't have to fill out a production sheet or track the technology on his ships.

Space Empires: Replicators also includes hex-sized terrain tiles for planets, asteroids, nebulae, and other permanent terrain effects. When an exploration marker reveals a terrain effect that stays on the map, the exploration marker is removed and replaced by a tile, giving the map a nice visual effect. (By removing the exploration marker, this also creates more room in the hexes because now the entire hex is the terrain.) For epic games, the backs of some of these tiles can be used to connect two Space Empires Boards.

New Deep Space terrain is included in this expansion, with the Galactic Capital (which comes with its own scenario), Regional Map, Gravitational Anomaly, Space Pirates, and the Fold in Space.