The Spaniard took his tally of career titles to 20 after winning his third final in four years on the clay centre court at the Buenos Aires Lawn Tennis Club.
"It's very hard to obtain two titles from one year to the next, tennis is smiling on me and I'm happy for that," the 30-year-old said in a courtside interviewer.
"I've always preferred even numbers to odd ones, but I never thought I'd reach a figure like this on the ATP (tour).
"It's been a great week for me and I must recognise that David is a great champion," Swiss Wawrinka, ranked 17th, said after receiving the runners-up trophy.
It was a fifth consecutive Spanish win in Buenos Aires after victories for Tommy Robredo in 2009, Juan Carlos Ferrero in 2010 and Nicolas Almagro in 2011. David Nalbandian was Argentina's last winner in 2008.
- Sports & Recreation
- Buenos Aires Lawn Tennis Club
- Buenos Aires