The Argentine corralled his 14th career title and first of the year with a 7-6 (7-2), 6-3 triumph over Benneteau in a 1-hour, 37-minute affair at the Rotterdam event.
Del Potro suffered a nose bleed between the eighth and ninth games of the final set, but quickly returned to serve out the match at love.
He was the runner-up in Rotterdam last year to Roger Federer, who was bounced by Benneteau in the quarterfinals of this year's edition.
The Frenchman remained winless in ATP finals -- he now has the most finals appearances without a title among active players at 0-8.
Swim Week Miami Beach 2014 [PHOTOS]