Having hit his ball into trouble with his second shot on the par-5 18th hole in regulation play, Johnson saved par to force a playoff with LIV Golf newcomers Joaquin Niemann and Anirban Lahiri.
On his 54th hole, Lahiri missed a seven-foot eagle putt for the win. He squandered this golden opportunity which would've banked him $4 million.
In the playoff, all three players went back down the 18th. Johnson found the bottom tier of the putting surface with his second shot, while Lahiri was greenside for two.
Niemann found a fairway bunker short of the green and the young Chilean was unlikely to make a birdie. It proved not to matter as the 38-year-old Johnson rattled in his eagle to seal victory at The International.
It was the two-time major champion's first win on the LIV Golf Tour and alongside Pat Perez, Patrick Reed and Talor Gooch, 4 Aces won their third consecutive team event too.
"It was going a little fast, but it was a good line! I felt like I played really well all week, I got some unlucky breaks here (18th hole) the first time around, so it owed me one and I got it," Johnson said on Sunday.
"You know the guys are playing different holes, so you've just got to handle your business. It doesn't really matter, I knew I needed a birdie on 18 in regulation.
"I felt like I hit a really good drive and hit a really good second shot - I made a good five to get in the playoff and then obviously made a really nice putt there."
Win: Dustin Johnson - $4,000,000
P-2: Joaquin Niemann - $1,812,500
P-2: Anirban Lahiri - $1,812,500
T4: Cameron Smith - $1,012,750
T4: Lee Westwood - $1,012,750
6: Talor Gooch - $800,000
7: Jason Kokrak - $675,000
8: Abraham Ancer - $625,000
T9: Louis Oosthuizen - $560,000
T9: Kevin Na - $560,000
T9: Sergio Garcia - $560,000
12: Branden Grace - $450,000
T13: Matthew Wolff - $315,000
T13: Sadom Kaewkanjana - $315,000
T15: Pat Perez - $240,667
T15: Bernd Wiesberger - $240,667
T15: Charles Howell III - $240,667
T18: Ian Poulter - $215,333
T18: Richard Bland - $215,333
T18: Bryson DeChambeau - $215,333
T21: Martin Kaymer - $171,200
T21: Laurie Canter - $171,200
T21: Paul Casey - $171,200
T21: Scott Vincent - $171,200
T21: Cameron Tringale - $171,200
T26: Matt Jones - $161,000
T26: Carlos Ortiz - $161,000
T26: Brooks Koepka - $161,000
T26: Jediah Morgan - $161,000
T30: Harold Varner III - $152,000
T30: Phachara Khongwatmai - $152,000
T30: Chase Koepka - $152,000
T30: Marc Leishman - $152,000
T30: Patrick Reed - $152,000
T35: Charl Schwartzel - $144,000
T35: Eugenio Lopez-Chacarra - $144,000
T35: Shergo Al Kurdi - $144,000
38: Sam Horsfield - $140,000
39: Graeme McDowell - $138,000
T40: Phil Mickelson - $134,000
T40: Hudson Swafford - $134,000
T40: Shaun Norris - $134,000
43: Wade Ormsby - $130,000
T44: Peter Uihlein - $127,000
T44: Adrian Otaegui - $127,000
46: Turk Pettit - $124,000
47: James Piot - $122,000
48: Sihwan Kim - $120,000
Win: 4 Aces (Talor Gooch, Dustin Johnson, Pat Perez, Patrick Reed) $3,000,000
2: Crushers (Bryson DeChambeau, Paul Casey, Charles Howell III, Anirban Lahiri), $1,500,000
3: Majesticks (Sam Horsfield, Ian Poulter, Lee Westwood, Shergo Al Kurdi), $500,000