Immelman held it together around Amen Corner and stretched his lead to as many as six shots on the back nine, taking the life out of a Masters that began with so much hype.
A two-putt par on the final hole gave him a 3-over 75, matching the highest final round by a Masters champion. Even so, it was good enough for a three-shot victory over Tiger Woods, whose hopes for a calendar Grand Slam ended with a thud.
Woods never got within five shots of the lead when he was on the course, twice missed birdie putts inside 8 feet and had to settle for a 72 and his second consecutive runner-up finish in the Masters.
"I learned my lesson there with the press," said Woods, who started the talk about a Grand Slam by stating three months ago that winning all four majors in the same year was "easily within reason."
The only slam possibilities now belong to Immelman, a 28-year-old with a polished swing, who finally realized his potential in the wicked wind of Augusta and a final round that yielded only four rounds under par.
Immelman, who finished at 8-under 280, started the week by playing a practice round with his boyhood idol, Gary Player, who won his third Masters in 1978 and set a record by playing for the 51st time.
Player told Immelman he was good enough to win the green jacket, and he left him a voicemail Saturday night that Immelman played on his speaker phone for his family to hear. The message: "I know you're going to win."
"He's been on me all week, telling me to believe in myself," Immelman said. "He also told me to keep my head still on putts. It's really a special moment, and I'm glad I pulled it through for him."
Immelman's wife, Carminita, and their 1-year-old son were waiting for him behind the green. Jacob took hold of the 18th flag, fussing when he couldn't go into the scoring shack to be with his father.
Immelman's parents also were there to greet him with hugs behind the 18th green. His father, Johan, is the former commissioner of the Sunshine Tour in South Africa.
"It's his moment, not mine," said the father, who waved away a reporter.
No one doubted he was capable of winning a major, but maybe not this one. Only four months ago, doctors discovered a tumor in his diaphragm that required surgery through his back to remove it. The tumor was benign and the recovery was quick. It hit warp speed this week at Augusta, where Immelman had only broken par once in his five previous Masters.
But he built a two-shot lead with three rounds in the 60s, and held it together during a few nervy moments.
Immelman made a 10-foot par save from the bunker at No. 9 to keep a two-shot cushion, but he continued to look shaky. His missed the 11th green well to the right, his chip didn't quite reach the green and he was left with a 20-foot putt that was slick and dangerous.
Ahead of him, Woods was gaining momentum.
Woods holed a 70-foot birdie putt on the 11th, made an acrobatic escape from the trees on the 13th and spun a wedge down the slope on the par-5 13th that left him 5 feet away for birdie.
Immelman holed his par putt. Woods missed, just as he has done the last two years on the back nine of a major he once dominated. Brandt Snedeker and Steve Flesch, the last two players with any hope, folded quickly.
Woods closed with a 72 and has finished third, second and second in his last three Masters. It also was his fifth runner-up in a major.
Immelman earned $1.35 million for his second PGA Tour victory, with Woods also finishing second behind him two years ago in the Western Open.