After Tokiyori died in 1263, he assisted Tokimune, who was tokuso (the head of the main branch of the Hojo clan), together with Masamura HOJO and Sanetoki HOJO who became regents before Tokimune came to the age of manhood.
弘長3年（1263年）に時頼が没すると、泰盛は時宗が成人するまでの中継ぎとして執権となった北条政村や北条実時と共に得宗時宗を支えた。