After the death of his uncle, FUJIWARA no Norimichi, Morozane and his cousin, FUJIWARA no Nobunaga, fought over the regent post, but because Morozane cooperated with the Emperor who loved Kenshi very much and who was hoping to let his direct family line take over the throne instead of his younger brothers (Imperial Prince Sanehito and Imperial Prince Sukehito) who were not of Fujiwara origin, Morozane successfully took over the family headship from Nobunaga who served as the regent, the head of the Fujiwara clan, and Dajodaijin (Grand Minister).
叔父藤原教通の死後は従兄の藤原信長と摂関の地位をめぐって対立するが、賢子を寵愛し、藤原氏の血を引かない弟達（実仁親王、輔仁親王）ではなく、自らの直系への皇位継承を望んでいた天皇と協調し、摂関・藤氏長者、さらに太政大臣となった信長を差し置いての一座獲得に成功した。