He qualified for the 2017 European Senior Tour where he had two tournament wins and won the John Jacobs Trophy as the leader of the Order of Merit.

Dennis and Peter Fowler were tied after two rounds and a playoff was arranged on the 18th hole, played as a par three from the fairway.

He had six other top-5 finishes during the season and won the John Jacobs Trophy as the leader of the Order of Merit.

Nike Tour playoff record (1–0) *Note: The 2017 Senior Italian Open was shortened to 36 holes due to rain.

European Senior Tour playoff record (2–1) Note: Dennis never played The Open Championship.