And then he almost lost it.
This is his third PGA Tour win this season and ninth of his career.
Bridgestone is also Tiger's last chance to prepare for the final major of the calendar year: the PGA Championship next weekend in Missouri. His grandmother is one of his biggest supporters who navigated her way around the hills of Firestone using a walker in 90-degree heat.
The 36-year-old Australian golfer has stopped his cancer treatment to go into palliative care.
Woods, an eight-times victor at Firestone, electrified the gallery with three early birdies but in the end managed only a middling 68 on a course that was there for the taking, with soft greens allowing players to fire aggressively at the pins.
Justin Thomas enjoyed the flawless preparation for the defence of his US PGA Championship title with victory in the WGC-Bridgestone Invitational in Akron as Rory McIlroy's final round charge never materialised. "I'm in a pretty good position". McIlroy finished the front nine with consecutive bogeys and never recovered.
Tommy Fleetwood, who had shared the second-round lead with Poulter, shot 74 to fall back to seven under.
Tiger Woods, an eight-times champion at Firestone, battled to a 73 and fell 11 strokes behind. Thomas had a couple of early setbacks but was commanding thereafter, plotting his way round the treacherous terrain so efficiently that he shot a 67 and finished with a three-stroke lead at 14 under par.
"We're obviously doing a lot of things right". "But it is what it is, and on to next week".
Justin Thomas tried valiantly to have Jarrod Lyle's yellow bucket hats shipped to OH so the world's best golfers could wear them during the WGG-Bridgestone Invitational. We underrate how hard it is to present sufficient encores to elite seasons (which is what past year was), but Thomas has made it look fairly simple with maybe the most complete game on tour. He lost in the semifinals of the Match Play.
Justin Thomas poses with the Gary Player Cup trophy after holding his nerve to win the Bridgestone Invitational. As if further validation was needed, Thomas' 394-yard blast on the final hole Sunday seemed to verify his code name for the club. "The golf course is playing very soft, very receptive".
Sweetest of all was seeing his grandparents, especially the embrace after he tapped in for par to finish at 15-under 265.
So ended a finale at Firestone that otherwise lacked drama.
The South Korean, who has three top-10 British Open finishes, said: "Winning this tournament has always been my goal for the year". I was so far back that I had to play a great round just to get in the top 10.
"My grandpa is not emotional, but I hadn't seen him smile or be that happy, maybe ever". I loved playing here, even when it was the World Series of Golf.