The club entered into the Yorkshire Football League for the 1965–66 season, joining Division Two. It took just two years for Denaby to achieve promotion to Division One, and in 1968 they just missed out on winning the league championship, finishing runners-up. They were relegated from the top flight in 1979, and by 1981 found themselves in the Third Division for the first time. In 1982 the Yorkshire League merged with the Midland League to form the Northern Counties East League (NCEL) and Denaby were placed in Division One South after finishing second in their final Yorkshire League Division Three campaign.