Favored by his elder half brother Koretada & by FUJIWARA no Kanemichi, Tamemitsu leapfrogged to Gon Chunagon (a provisional vice-councilor of state) in 973 over senior six Sangi, and he also received the investiture of Jusanmi (Junior Third Rank) at the same time.
異母兄である伊尹・藤原兼通から可愛がられ、天延元年（973年）に先任参議6名を飛び越して権中納言に抜擢され、同時に従三位に除せられる。