As recorded in the 'Kansei Choshu Shokafu' (A record of family trees of samurai warriors of Edo bakufu), the Mizuno clan is thought to have been from the MINAMOTO no Mitsumasa line of Seiwa-Genji (Minamoto clan); however, there are different theories as to their origin as some of families call themselves the Fujiwara clan and other families who became Owari clansmen call themselves the Kanmu-Heishi (Taira clan).
水野氏の出自は「寛政重修諸家譜」に従い清和源氏源満政流とされているが、藤原氏を称したり尾張藩士となった家に桓武平氏を称するものがあったりすることから、源氏と断定できず諸説ある状態である。