Nadal shared two tightly competitive sets with his opponent before turning on the style in the decider for a 7-5 5-7 6-0 win for his first tour title of the year.
The Spaniard’s win also ensures he matches world number one Novak Djokovic by winning his 28th career Masters title.
Victory capped a stunning week for Nadal, who has struggled for form since taking seven months out because of a knee injury, and withdrew from last month’s Miami Open due to a virus.
An exhilarating first set highlighted by a series of lung-bursting rallies saw both men swap two breaks apiece before Nadal struck again to edge in front.
Nadal twice dragged himself back from a break down in the second before Monfils somehow summoned the energy to break his opponent for a third time to serve out to level the scores.
But hopes of a fitting climax were shattered in the second game of the decider when a clearly ailing Monfils sent down two consecutive double-faults to give Nadal the early break.
And showing few ill effects from his recent periods of inactivity, Nadal stepped up to power his way to victory and send a message to his opponents that he is on the road to recovery.