The affable Irishman also increased his chances greatly of playing in his first Ryder Cup this September.
Paul McGinley comments on his win
McGinley outlasted Darren Lee and Paul Lawrie in the forced conclusion, following a decision by tournament officials to shorten the event from the scheduled 54 holes to just 36.
Heavy rains and a soaked Celtic Manor led to the ruling, and it was decided that the short par-3 12th would be the hole of choice for the playoff.
Originally tied at 6-under-par 138, Lawrie was the first to slip in overtime, when the former British Open champion made bogey on the second extra hole.
Lee had a great opportunity to win on the fourth hole, when he was faced with a putt of just six feet for the win, but watched in shock as it lipped sharply out to the right.
On the fifth hole, both Lee and McGinley hit their tee shots into bunkers.
Yet while McGinley was able to blast his shot out to a foot, Lees second did not make the green.
Putting from the fringe for par, the Englishman left the attempt a bit short, giving the title to McGinley.
It was the most tension packed situation Ive been in because a lot of pressure came from within,' said McGinley. 'But it was pressure I felt I could handle and came through. I wasnt over-awed by it and I just felt unbelievably determined to do it.'
While prize money was reduced by 75 percent because of the shortened play, the 34-year-old McGinley made a huge move from No. 10 to No. 8 on the all-important Ryder Cup points list.
Should he hold on in the top-10 through the next four weeks, he will be competing in his first Ryder Cup in nine full seasons on the European Tour.
Said the champion: Everybody knows how much I want to play in the Ryder Cup. Everybody knows what position I have been in, and I feel very fulfilled that Ive done what I set out to do, not 100% yet. I still have to finish the job off but I have broken the back of it now.
Click here for full-field scores from the Celtic Manor Resort Wales Open