The competition, the entire final of the tour, was decided on the very last green.
Cantley was in the lead all weekend but trembled a little on the cuff and made a bogey on the 17th hole.
But in the 18th, the 29-year-old American played all the more confident and was able to putt for a birdie and final victory, one stroke ahead of the Spanish world setter Jon Rahm at East Lake Golf Club in Atlanta.
And that despite the fact that Rahm in the competition itself was three strokes better than Cantley.
Because after a couple of weeks of competitions where all players except the top 30 were knocked out - Alex Norén missed the final last weekend with only two strokes - Cantlay had to go out with two kinds of lead against the then runner-up Tony Finau.
Others in the field were further behind, based on how they were in the summary.
And that lead became absolutely decisive.
Second place Jon Rahm started four strokes behind, third Kevin Na a full eight strokes behind.
The two were best in terms of games with 266 strokes (14 under par) and can take comfort in the fact that they too are richly rewarded - they get five and four million dollars respectively for their efforts.
The only Nordic participant in the competition, the Norwegian Viktor Hovland, went like Cantley the four days at -11, finished split five and gets a check for 2.2 million dollars from Atlanta.