'It's been a great week here with my family but a tough one on the golf course today,' said Goosen. 'I struggled with my swing and I think I used all of the golf course to get this job done.'
Paul McGinley was Goosen's closest challenger over the weekend, and despite pulling within one of the lead early on the back nine, he finished four shots off the pace alone in second at 14-under-par 270.
Goosen, who also won this event in 2000, played brilliantly in what was the final edition of the tournament. He carried a three-shot lead into the final round at Saint-Nom-La Breteche Golf Club and knocked his second shot inside 10 feet for a birdie at the first.
The South African kept on rolling and hit his approach to 12 feet at the fifth. Goosen drained the putt but stumbled at the very next hole with a bogey.
Goosen recovered with a birdie at the par-3 seventh after his tee shot stopped eight feet from the cup to put the reigning Order of Merit champion at 19 under par.
McGinley was making a charge, however, despite a bogey at the opening hole. He tallied a birdie at the fifth and another at the eighth to make the turn at minus-15.
The Irishman picked up another birdie at the 10th and landed his second shot inside six feet at the 11th to make it two in a row.
Meanwhile, Goosen, who was playing alongside McGinley and Nicolas Colsaerts in the final group, found trouble off the tee at the 11th. His drive went into the trees and Goosen's second stayed in the thick rough.
Goosen hit his third on the putting surface and two-putted for a bogey to fall back to 18 under, one shot clear of McGinley.
Goosen kept his calm demeanor and hit his tee shot to 14 feet at the par-3 12th. He drained the putt for a birdie and made it two straight with a birdie at the 13th to jump to minus-20.
McGinley fell apart down the stretch with a bogey at the 15th and a double bogey at the par-5 16th to fall out of contention and Goosen coasted to the winner's circle, despite two bogeys of his own over the last five holes.
'The course was starting to play tough on the back nine and I got a break on the 16th when Paul made double bogey,' said Goosen.
McGinley closed his round with a bogey at the last to finish alone in second after a round of even-par 71.
France's own Raphael Jacquelin shot a 4-under 67 to finish five shots back in a tie for third with Ian Poulter at 13-under-par 271.
Colsaerts was one shot further back at 12-under-par 272. He was joined by Hennie Otto in a tie for fifth.