Fire Emblem Gaiden was a short side-story to the previous game and second to be released on the Famicom, being the second game in the series. Like it's prequel, it was only released in Japan.

Gaiden is set on a different continent and occurs at the same time as Ankoku Ryu to Hikari no Tsurugi. It was only five chapters long, but introduced many new aspects to the series, some of which were kept, while others were dropped quickly. The story follows Alm and Cellica as they discover their heritage.