Jankovic, the No.1 seed and defending champion, broke in the first game of the match, but from there the No.5-seeded Garcia took over, breaking right back and never falling behind again, taking six of the next eight games to take the first set then breaking early in the second set en route to a 3-1 lead.
Jankovic caught up to 3-all but Garcia broke again and eventually served out the match, firing back-to-back aces to bring up match point then hitting a phenomenal forehand winner to shut the door, 63 64.
Going into the match Garcia was 0-6 lifetime against Top 10 players, but had come very close in her two previous head-to-head meetings with Jankovic - in fact she held match points in both meetings.
"I'm very happy to win my first WTA title," Garcia said. "It was a good week for me. It's never easy playing with the altitude - it's hard to adapt, and my level was going up and down throughout the week - but I think I adjusted well and I probably played my best match of the week today in the final.
"I'm also really happy I was able to beat Jelena in the final. She's a really nice girl and a great player - she was the No.1 player in the world - and I had to play the best I could today to beat her.
"To win a WTA title is always a goal. Today is the best day I could imagine."
By virtue of the result, Garcia skyrockets past her previous career-high ranking of No.69, shooting from No.74 in the world to No.51 - now just one spot away from breaking the Top 50 for the first time.
And while winning her first WTA title is amazing enough, by winning the Claro Open Colsanitas doubles title on Saturday with Lara Arruabarrena, Garcia became the first player in nearly two years to pull off a singles-doubles sweep at a WTA-level event - the last one was Serena Williams at the Olympics.
With Alizé Cornet winning in Katowice, this is also the first time in six and a half years that two Frenchwomen have won WTA titles in the same week. The last time was the week of October 1, 2007, when Virginie Razzano won Tokyo [Japan Open] and Pauline Parmentier prevailed in Tashkent.