In January 1599, as his younger brother (born from the same mother) and Ieyasu's seventh son, Matsuchiyo, died early, Tadateru inherited the reigns of the Nagasawa Matsudaira family and was given the Fukaya Domain which was 10,000 koku (crop yield) in Musashi Province.
慶長4年（1599年）1月、同母弟で家康の7男・松千代が早世したため、その後を受けて長沢松平家の家督を相続し、武蔵国深谷藩1万石を与えられた。