Even after Yoritomo died, Tokimasa remained influential in the bakufu as the grandfather of Yorimoto's sons MINAMOTO no Yoriie and MINAMOTO no Sanetomo, and became the first regent.
頼朝亡き後もその子源頼家・源実朝の外戚として幕府内で強い影響力を持ち、初代執権となった。