Standing behind the green -- as always -- was his wife, Amy, with her long blonde hair and easy smile, their three children at her side.
She had not been on a golf course since being diagnosed with breast cancer 11 months ago, and had stayed in bed most of the week.
"I wasn't sure if she was going to be there," Mickelson said.
A week of roars gave way to tears as they hugged for the longest time. Mickelson finally had to let go, and with a single tear trickling down his cheek, headed for the scoring hut to sign his card for a 5-under 67, the official stamp on a most compelling Masters.
"It's one of the best things that we've gone through," he said of the embrace. "In the last year, we've been through a lot and it's been tough. And to be on the other end and feel this kind of jubilation is incredible."
This Masters deserved nothing less than a storybook ending.
It began with Tiger Woods returning from a sex scandal, which shattered his image but left his game intact. He captivated crowds by flirting with contention until the putts stopped falling and he tied for fourth. It ended with Mickelson making daring escapes from the trees, delivering a clutch birdie in the heart of Amen Corner, and pulling off a high-risk shot out of the pine straw.
He knocked in an 8-foot birdie putt for a three-shot margin over Lee Westwood, who lost the lead for good with a three-putt bogey on the ninth hole and never got closer than two shots over the final six holes.
"It's been such an incredible week, an emotional week," Mickelson said. "And to cap it off with a victory is something I can't put into words. It's something we'll share for the rest of our lives."
Mickelson finished at 16-under 272, the best score by a Masters champion since Woods in 2001.
Just like his last Masters title in 2006, the outcome was never in doubt as Mickelson arrived on the 18th green. Unlike any of his other 40 victories around the world, there was never this much emotion.
Mickelson shared a long embrace with his caddie, Jim "Bones" Mackay, who took countless trips to San Diego to be with Mickelson as he coped with the uncertainty of cancer -- not only Amy's but his mother, Mary, who was diagnosed the week of his wife's first surgery.
Mackay sat on the grass, legs crossed like a schoolboy, during the green jacket ceremony. He could barely speak.
"Twenty years from now, nothing will compare to this," Mackay said.
Westwood was third at the British Open last summer, tied for third at the PGA Championship, and dealt with another close call at the Masters with his highest finish ever in a major. He remains among the best players without one.
"Phil, being the champion he is, hit some great shots coming down the stretch," said Westwood, who closed with a 71. "He's been through hard times recently, and he deserves a break or two."
Anthony Kim closed with a 65, the best score of the tournament, and finished alone in third.
Mickelson became the eighth player with at least three Masters titles, and it was the fourth major of his career, breaking out of a pack that had included Ernie Els, Padraig Harrington and Vijay Singh from his generation.
The signature moment came on the 13th, a hole Mickelson has dominated like no other at Augusta. With a two-shot lead, he was stuck between two Georgia pines and had just over 200 yards to the hole. He never considered anything but a shot at the green.
"I was going to have to go through that gap if I laid up or went for the green," Mickelson said. "I was going to have to hit a decent shot. The gap ... it wasn't huge, but it was big enough, you know, for a ball to fit through.
"I just felt like at that time, I needed to trust my swing and hit a shot," he said. "And it came off perfect."
Woods was perfect at times, holing an 8-iron for eagle on the seventh hole, the start of an eagle-birdie-birdie stretch that took him from seven shots behind to having some hope.
But not for long.
Woods hit into the trees on 11 and struck a pine trying to escape to make bogey on the 11th. The end came on the 14th, when he missed a 6-foot birdie putt to stay in the game, then missed the next one for a shocking three-putt bogey.
Asked to sum up his week, Woods said in a terse interview with CBS Sports analyst Peter Kostis, "I finished fourth."
"It's not what I wanted," he said. "I wanted to win this tournament. As the week went on, I kept hitting the ball worse."
Asked about his dour mood as his game got away from him, Woods said, "People are making way too much of a deal on this." He also said he did not know when he would return, saying he needed time off to evaluate.
For Mickelson, it's a celebration to remember.
He says his wife's longterm outlook is good, but the medication has taken a toll on her emotions. They arrived Tuesday, but she stayed in bed most of the week at the house they rented. Even in the final moments, no one was sure if she was coming to the course until she walked toward the 18th green with Mackay's wife, Jennifer.
"I didn't really want to look up because I knew I'd get choked up if I saw her," Mackay said. "It was great to see her there, for sure."
Mickelson was the only player among the top 10 to play without a bogey in the final round. Just when it looked like it might slip away from him, Lefty came through with two par saves from the trees on No. 9 and No. 10, then pulled away with the clutch 9-iron on the 12th to 15 feet behind the hole.
Woods teased with contention by making two eagles in one round for the second time this week. Most of the day, however, he was always too many shots back to scare anyone.
Whatever doubts there are about Woods as a person, his golf doesn't appear to be suffering. It was his first competition in five months, his first time in public since he became tabloid fodder for his rampant infidelity. Yet he performed as if he had never been gone.
Choi's only consolation was going all four rounds with Woods at Augusta and matching his score. He wanted much more, and for the longest time was poised to give Asia successive majors following Y.E. Yang's win at the PGA Championship.
He unraveled on the 13th, a hole where he had made birdie the previous three rounds. From the fairway, he tugged his approach into the back bunker, leaving him a frightening shot down a steep slope toward Rae's Creek. He barely got it out of the sand, then three-putted for a bogey. Another bogey followed on the 14th.
Kim, who set a Masters record last year with 11 birdies in the second round, came out of nowhere. He played a four-hole stretch starting on the 13th in only 11 shots -- an eagle and three birdies -- and finished with two strong pars to post at 12-under 276.
His only hope was for Mickelson to fade. That wasn't about to happen.