The Spanish star made a 7-foot birdie putt on the par-5 18th'the only hole used for the playoff at Sheshan Golf Club'after the Englishman missed a 10-footer.
Garcia forced the playoff by holing a 5-foot birdie on 18 to finish with a 4-under 68 and match Wilson at 14-under 274. Wilson, a surprise star for Europe in the Ryder Cup, reached the playoff by saving his par on 18 with a 7-footer for a 70.
Wilson was attempting to win his first European Tour title.
The finish moved Garcia into the No. 2 spot in the world rankings behind Tiger Woods, pushing Phil Mickelson to No. 3.
Mickelson, the 2007 champion, shot a 73 to tie for eighth in the $5 million tournament, five strokes behind the leaders.
Peter Hanson (66) and Geoff Ogilvy (70) finished a stroke off the lead, while Henrik Stenson (71) was three behind.
Garcia and Wilson were the survivors on the back nine, which saw four players ' Garcia, Wilson, Hanson and Ogilvy ' tied at 13 under over the closing holes.
All play was washed out Friday, and rain slowed the start on Saturday which forced the Monday finish. Wilson played two holes of the final round on Sunday, and Garcia got in three before darkness stopped play.
With victories this season in The Players Championship and his home-course Castellon Masters, Garcias consistency has moved him up the rankings. He also has finished second or tied for second in three events this season.
This event is the first of the 2009 European Tour season, which will end next November in the Dubai World Championship. The European Tour also rebranded the Order of Merit ' the season money title ' and now calls it the Race to Dubai. That tournament will have a $10 million purse with $10 million more available in bonus money.