'It hasn't really sunk in,' said Poulter. 'I refused to lose.'
Poulter and Garcia traile Alastair Forsyth by three shots heading into Sunday's final round but quickly found themselves back in the mix after Forsyth bogeyed the first two holes. When all was said and done, Poulter and Garcia had carded matching rounds of 70 to finish regulation at 7-under-par 277.
Back to the par-4 18th, both players hit poor drives but Poulter ended up in much better shape than his challenger. Garcia managed to advance his ball but could not get out of the rough. His third shot died before it reached the putting surface and he chipped his fourth within 4 feet of the hole for a bogey.
Poulter knocked his approach to the edge of the green and pitched to 3 feet. He converted the short par attempt and celebrated his sixth career victory on the European Tour with a fist pump.
'It's a dream end to what was, I felt, an average year,' said Poulter.
Poulter grabbed his first share of the lead on Sunday with a birdie at the par-4 second. He stumbled with back-to-back bogeys from the fourth, however, to fall behind Forsyth again, but it was only a matter of time for Poulter to return to the top of the leaderboard.
Forsyth's final round stalled as Poulter and Garcia battled for position. Poulter moved to 6 under with a birdie at the eighth and converted a 15-footer for a birdie at the very next hole to join Forsyth in the lead. Poulter then drained a long birdie putt at the par-4 10th to move into first place alone.
Poulter missed the green at the par-4 13th and hit an awkward chip that stopped 20 feet from the hole. He missed the putt for a bogey and just like that was in a three-way tie with Forsyth and Garcia, who had birdied two in a row starting at the 11th.
Neither player made a move down the stretch, but Forsyth took himself out of the running at the 16th. He tried to hit his second shot underneath and through a row of trees but his fate was announced by the thump of his ball against a trunk.
Forsyth bogeyed the hole to fall back to 6 under, but Poulter and Garcia were unable to shake each other. Garcia had a short birdie try at the last, but failed to convert and Poulter joined the Spaniard in the playoff as he missed a birdie try of his own at the 18th.
Garcia could not keep up with Poulter in the extra session and the Englishman, who has now won every year on the European Tour since 2000, prevailed.
Forsyth, who was seeking his first title since 2002, finished alone in third place at 6-under-par 278 after a round of 74.
Peter Hanson made it four straight days with a 70 on Sunday, taking fourth place at 4-under-par 280. David Howell and Christian Cevaer followed at 3-under-par 281.
Lee Westwood and Scott Drummond shared seventh place at 1-under-par 283 while Paul Casey and Trevor Immelman tied for ninth at even-par 284.