The second-seeded Monaco defeated the seventh seed 7-5 4-6 6-3 in a match that ran to more than three hours to claim his fourth title of the season and boost his chances of qualifying for the end-of-year Barclays ATP World Tour Finals.
Monaco recovered from 0-2 down to take an 81-minute opening set, although the 28-year-old might have moved ahead in the match earlier had he converted two set points at 5-3.
Benneteau, still seeking a maiden ATP crown at the age of 30, hit back in the second, breaking twice to Monaco's once to set up the decider.
But Monaco turned the screw in the third, breaking for a 4-2 lead and holding his next two service games to wrap up a hard-fought victory.
Defeat for world number 34 Benneteau leaves him nursing an unwanted 0-7 record in ATP finals.