After the Imperial Court broke into the Northern and Southern courts, Moromoto belonged to the Southern Court and served as Kanpaku (Chief Advisor to the emperor) under Emperor Gomurakami subsequent to 1351, being one of the heavyweights of the Southern Court government.
南北分裂後は南朝(日本)方に属し、正平6年（1351年）以降、後村上天皇の下で関白をつとめるなど、南朝政権の重鎮のひとりであった。