Garcia defeated Finland's Mikko Ilonen on the third hole of a sudden-death play-off to make up for missing out 12 months ago, when England's Chris Wood made an eagle on the 72nd hole to beat Garcia and George Coetzee by a shot.
A flawless closing 65 saw Garcia set the clubhouse target of 16 under par, but the 33-year-old crucially missed from eight feet for a birdie on the last and then looked on as Ilonen birdied the 16th and 18th to complete a 66 and force extra holes.
The players returned to the 18th for the play-off and both found the green on the par five in two, Ilonen missing his eagle attempt from 25ft before Garcia did likewise from half the distance.
A second visit to the 18th failed to identify a winner, Ilonen missing an eagle attempt from 25ft after Garcia had got up and down from a greenside bunker.
However, the third extra hole proved decisive as Ilonen found the same bunker and was unable to rescue a birdie, leaving Garcia a tap-in to secure an 11th European Tour title after his long eagle putt had narrowly missed.
Thorbjorn Olesen had a great chance to join the play-off but missed from 12ft for an eagle on the 18th, the Dane sharing third place with joint overnight leader Rafael Cabrera-Bello.
Cabrera-Bello also needed an eagle on the 72nd hole to catch Garcia and Ilonen, but saw his chip from over the green pull up three feet short of the hole.
"It feels good," said Garcia, who will move from 11th to inside the world's top 10 when the rankings are updated on Monday.
"It's funny because I started the day thinking if I can shoot six or seven under maybe I can have a chance, and it turns out I had a very similar putt that I had last year to get it to 17 under on 18; I hit a good putt and unfortunately it didn't break.
"The up and down from the bunker in the play-off was key and I'm very happy to be able to win it."
Asked about the pressure of contesting his seventh European Tour play-off - having won two and lost four - Garcia added on Sky Sports: "I almost feel less pressure because you feel like you've had a great week already and if you win it's kind of like a little bit of a bonus.
"It's been an amazing week already and I was definitely more nervous on my tee shot on the 18th (in regulation) than in the play-off. That's probably why I hit three better tee shots."