Blue Moon is a cold country east of Orange Star. Their relationship with Orange Star is a testy one--at times the two nations are fighting each other, at other times they battle alongside each other to defeat a common foe.
- Olaf: A Blue Moon CO who used to side with Orange Star. His units are strong in Snow and move through without movement penalty, but is weak in Rain.
- Grit: A Blue Moon CO who left Orange Star to join Blue Moon. His Indirect Combat Units have higher firepower and +1 added to their firepower range. Direct Combat units are weaker though.
- Colin: A Blue Moon CO. His Units are cheaper to deploy than all other COs, but has lower firepower due to inexperience.
- Sasha: A Blue Moon CO and Colin's Sister. Properties under Blue Moon's control yield an extra 100G when she is in command.
 Advance Wars
In the first Advance Wars game, Blue Moon starts off as the country attacking Orange Star, thus giving Orange Star the alibi that Sonja uses to prove to Eagle that the Andy that he saw was an imposter. After being forced out of Orange Star, Blue Moon does not do much until the final chapter of the game, where a Blue Moon base has been set up to help defeat Black Hole and the commanding CO Sturm.
In the second Advance Wars game, Blue Moon and Yellow Comet are the two countries that are available after Orange Star. In Black Hole Rising, Blue Moon gets a new CO, Colin. The main attacker of Blue Moon is Lash. After liberating Blue Moon, the Blue Moon COs join the Orange Star COs in freeing Yellow Comet. However, if Yellow Comet is freed first, then Blue Moon will instead receive Yellow Comet's aid, instead of aiding them.
Blue Moon isn't able to aid in the Allied Liberation of Green Earth, but can serve as a valuable asset in the final two missions.
 Advance Wars: Dual Strike
In the third Advance Wars game, Blue Moon receives a new CO: Colin's older sister Sasha, and she and Colin join the group fairly early. Blue Moon's color scheme is the color scheme for the army in the second position, no matter what the CO. Blue Moon CO Grit will join the group along with Sami, Sonja, and Eagle in Chapter 23, which starts the final stretch of the game. The Blue Moon CO Olaf does not appear personally in the game since he stayed behind in order to rebuild his hometown. A clone of Olaf does appear in the game, however, and is the first clone the group fights.