Harkins finished tied for 59th at the
2016 U.S. Open. At the end of 2016, aged 30, Harkins finished 53rd in the Web.com Tour qualifying tournament. This earned him conditional status for the 2017 season. He finished his first Web.com Tour season in 21st place, and was promoted to the PGA Tour for 2018. Harkins claimed his first professional victory in November 2021 at the
TaylorMade Pebble Beach Invitational. He won by two shots ahead of
Alex Čejka and
Harry Hall. In January 2022, Harkins won his first Korn Ferry tour event at
The Bahamas Great Abaco Classic. Harkins won in a playoff over
Dou Zecheng. This was Harkins' first win in 134 Korn Ferry starts. ==Professional wins (3)==