[1] Upon his father Hojo Ujiyasu's retirement, Ujimasa inherited formal leadership of the family around 1559.

[2] In 1560, Hojo clan seized Iwatsuki Castle and almost conquered whole Musashi Province.

In 1577, Ujimasa invaded Kazusa Province and realized the reconciliation with his old enemy, Satomi Yoshihiro.

He invaded the territory of the Takeda clan in Suruga from both sides attacked Katsuyori, which triggered the Battle of Omosu and later join attack on Conquest of Koshu, from the east of Kai province at Battle of Tenmokuzan in 1582.

[2] Like many samurai who committed seppuku in the face of shameful defeat, Ujimasa composed death poems: (雨雲の おほへる月も 胸の霧も はらひにけりな 秋の夕風) (我が身今 消ゆとやいかに 思ふべき 空より来たり 空へ帰れば) Hōjō Ujimasa appears in Koei's video games Kessen, Samurai Warriors 2, Samurai Warriors 3 and Warriors Orochi.

He is also in Capcom's Sengoku Basara 1 and 2 (including Heroes) as an old man who is armed with a spear and has both his ancestral spirits and ice attacks and assisted by Fūma Kotarō.

Professional wrestler Akito wrestled as Ujimasa for the Dramatic Dream Team promotion on February 10, 2013.