Monica Niculescu wins first title
Niculescu had been runner-up twice on tour before finally breaking through at the outdoor hard-court tournament in southern Brazil.
The 75th-ranked Romanian broke Puchkova's serve to go up 5-4 in the final set then converted on her service game to close out the match in 1 hour, 59 minutes.
"It's unbelievable," Niculescu said. "This means a lot, I was so nervous and wanted to win this so much. My game was not brilliant today, but it shows that in tennis if you keep fighting you can manage to win."
She broke Puchkova three times to win the first set but allowed the Russian to rebound in the second with two breaks of her own, including in the final game of the set.
The 109th-ranked Puchkova, who ended with six double faults, had upset top-seeded Venus Williams in three sets in Friday's semifinals.
"It wasn't easy, she was in form and in good shape after beating Venus," Niculescu said of Puchkova.
Niculescu, ranked as high as 28th early last year, was playing in her third final on tour, and first since a loss to Williams in Luxembourg last October. The 25-year-old Romanian had also made the final in Luxembourg in 2011.
Niculescu defeated seventh-seeded Kristina Mladenovic of France in the semis.
Puchkova, just two days younger than Niculescu, was also playing in her third final, and first since 2006. She had beaten third-seeded Kirsten Flipkens of Belgium in the first round to begin her run in Brazil.