Dennis earned his Legends Tour card at Q School in 2017 and later that year became the first American to win the John Jacobs Trophy for topping the Order of Merit, and was also named Rookie of the Year that same season.

 
After four top five finishes in the 2017 season, he secured his first title at the Senior Italian Open and just two tournaments later, he won his second event, the Dutch Masters.
 
Dennis defended his 2017 Senior Italian Open title and became the first two-time winner of the event before going on to claim the MCB Tour Championship – Mauritius by eight shots. Clark’s latest senior title came at the 2019 WINSTONgolf Senior Open, coming from six shots behind on the final day, recording a final round of 63, nine under par.