Monaco, the top seed, had twice finished a runner-up in Vina del Mar, but eventually proved too strong for his Argentine compatriot after a two hour, 46 minute encounter.
"It was a hard final," Monaco said afterwards. "At the beginning I felt I was playing very well.
"Then in the second set I started playing a little bit nervous and he came back, fought a lot, and at that time played really well.
"I tried to be very focussed, tried to fight for every point like it was the last one and I started playing better every game."
