He was adopted by his elder brother Tadamitsu MIZUNO, the lord of the Okazaki Domain, on February 10, 1699 and on October 19 he took over from Tadamitsu as the head of the family.
元禄12年（1699年）1月11日、実兄である岡崎藩主水野忠盈の養子となって、9月27日に家督相続した。