Because of earlier rain delays, 36 holes had to be played yesterday, and the 28-year-old shot two rounds of 70. Jamie Spence finished second and fellow Englishmen Martin Gates and Van Phillips shared third place with Raymond Russell a stroke further back.
Gates was Goosen's closest pursuer for most of the day but had a nightmare end to his final round. He had a bogey at the 15th and, at the 175-yard 16th, pushed his tee shot into the water for a double-bogey five.
Gates, who started the week in 177th place on the European money list with winnings of pounds 5,917 this season, compounded the errors by dropping another at the 17th and went into water again on the last, running up a bogey six.
Colin Montgomerie shot 73 and 69 to finish joint 11th on 10 under, and he gave an honest summary of his performance. "I missed a load of putts and didn't play very well in between," he said.
Goosen, the 1990 South African amateur champion, won the European Tour qualifying school two years later. He looked a superstar-in-the-making when he finished second in his first tour event, the 1993 Dubai Desert Classic, and won three times in his home country that season, but he had to wait until last year's Northumberland Challenge at Slaley Hall for his maiden European victory.
"I still have a lot to learn in this game," said Goosen, who is likely to try for his US Tour card at the end of this season.
"Watching Ernie [Els] play and seeing him do so well encouraged me to try to get up there as well. I don't set goals for myself except to improve.
"Good amateurs seem to play well in their first year (as a pro), then fade away and come back again."
Patricia Meunier Lebouc collected her second American Express Tour crown when she shot a final round of 71 to win the Guardian Irish Open at Luttrellstown Castle yesterday.
The Frenchwoman, winner of the 1994 English Open, beat the Spaniard Laura Navarro by one shot with the holder, Britain's Alison Nicholas, a further stroke adrift.
Scores, Digest, page 19