In the first Rotterdam final between two unseeded players since 2008, Monfils raced past his Swiss opponent to convert two break points on his way to sealing the opening set in 36 minutes.
Despite winning his opening game to love, Wawrinka was broken by Monfils in the third game, while the Frenchman also maintained his service rhythm to dictate play in the final set.
Monfils, the 2016 Rotterdam runner-up, converted another breakpoint to go 5-2 ahead before he served out the match for his eighth career ATP title.
World number 33 Monfils, who reached the Sofia Open semi-finals last week, credited his practice partner Wawrinka for his resurgence, having lost just twice in 11 matches this season.
“You know this win is part of him,” said Monfils, who last won an ATP title at the 2018 Qatar Open.
“We’ve been practising a lot, we’ve been talking a lot.
“… Sorry I beat you in the final. I hope we can have many more battles.”