The last time Westwood won on the European Tour was the Belgacom Open in 2000. That year he won six times on tour and finally unseated Colin Montgomerie atop the European Tour Order of Merit.
Things went downhill quickly for the 30-year-old. He started the 2001 season fourth in the World Golf Rankings but plummeted to 215th last week, with three top-10s in the last three years.
Westwood's fortunes changed Sunday at the Golfclub Mnchen Nord-Eichenried.
'I'm fairly emotional,' said a tearful Westwood, who picked up his 15th victory on the European Tour. 'It's been more than two years since I won. This is a big moment.'
Paul Casey (69), Andrew Coltart (68), Gary Evans (71), Peter Hedblom (67) and Raphael Jacquelin (71) shared third place at 15-under-par 273.
Westwood seemed to be out of the hunt for the title when he three-putted for bogey at the seventh. He birdied the ninth to reclaim the lost stroke, but made his move up the leaderboard with sensational play on the second nine.
At the 11th, Westwood drained a 12-foot birdie putt and one hole later, he sank a 10-footer to get within one shot of lead. Westwood knocked his approach from the rough at the 13th to less than a foot to set up a tap-in birdie and match Cejka and overnight leader Robert Karlsson in first place at 16-under par.
Westwood had good looks at birdie at both 14 and 15, but squandered his chances. Karlsson meanwhile fell off the pace with a pair of double-bogeys on the back side and Cejka dropped down the leaderboard at the 16th when he missed the green and hit a poor chip.
That left the door open for Westwood. He hit another wonderful approach to tap-in range at the 16th to take sole possession of first and from there, it was time to pad the lead.
Westwood missed the green at the par-3 17th, but chipped in for birdie. He left his second short at the par-5 18th, but chipped to four feet and rolled home the birdie putt to post his three-shot victory.
'I just enjoy winning and being in the lead with my name on the leaderboard and in front of people,' said Westwood. 'I have worked for three years to get back to here and there was no reason not to enjoy it while I was there today.'
Cejka, who plays most of his golf on the PGA Tour, mounted a serious charge at becoming the first German winner in the 15-year history of this event. He carded a 5-under 67 to take second place at 16-under-par 272.
Karlsson held a two-shot lead as Sunday's final round began but struggled around the turn. At the 10th, missed the green but flopped his chip to 10 feet. He ran that par putt three feet past the hole, then lipped out his bogey-saving putt.
He birdied the 11th but double-bogeyed the 16th when he found water and birdied the 18th to post a 2-over 74 on Sunday. He tied for eighth place with John Bickerton (71) and John Bickerton (71) at 14-under-par 274.
Thomas Bjorn, the 2002 champion, posted a 1-over 73 and was part of a tie for 17th place. Ernie Els fired a final-round 8-under 64 to join Bjorn in the logjam at minus-11.