On August 26, 2018, he won The Northern Trust for his first playoff victory; in the process, he established a new record for the tournament when held at the Ridgewood Country Club, with a score of 266, besting the old Ridgewood record of 270, which was set in 2014 by Hunter Mahan. The following week, he won at the Dell Technologies Championship played at TPC Boston in Norton, Massachusetts, with a final score of −16, two shots clear of Justin Rose. This put him over 2000 points ahead of the second place player, Dustin Johnson, in the FedEx Cup rankings. This margin secured him top seeding at The Tour Championship, regardless of his finish at the BMW Championship. This also marked his fourth win on tour, third for the year, and second during the playoffs. At the Tour Championship, DeChambeau finished 19th out of 30 participants. As a result, he fell to 3rd in the FedEx Cup, winning $2,000,000.
“I was literally thinking I’d need surgery but I talked to Greg, he was like no, no, no, don’t do any of that, we’re going to teach your body to tolerate the force. Usually when ligaments get torn or bones get broken or whatever it’s because the muscles aren’t functioning properly, so thats what I’ve been doing.” He’s been focusing on exercises that get him into “extreme positions of rotations and flexions” at which point he adds weight to build mental and physical tolerance in those positions.
THE PLAYERS Championship: After beginning the final round of THE PLAYERS Championship three strokes off the lead, at 7-under 209, played his last six holes in 6-under to post a 6-under 66 and join a three-hole aggregate playoff with 2008 PLAYERS champion Sergio Garcia and Kevin Kisner. Finished birdie-par-birdie-eagle-birdie-birdie on Nos. 13-18 in regulation. Played Nos. 15-18 in a 5-under total of 11 strokes. The four-hole score of 11 set a new single-round low for the final four holes at TPC Sawgrass. Previously, seven players had finished with a score of 12 on the final four holes. When Garcia was eliminated after the aggregate playoff, Fowler and Kisner returned to the famed, par-3 17th for sudden death. Fowler converted a 4-foot, 8-inch putt for birdie to claim the title. Before his back-nine charge, his mother had made her way to the airport to leave town. A text message alerting her to her son's rally resulted in her immediate return to TPC Sawgrass in time to witness the win. With the victory, moved to ninth in the Official World Golf Ranking and No. 7 in The Presidents Cup standings.
Lowry was the 2007 Irish Amateur Close Champion, defeating Niall Turner 4 & 3 in the final. While still an amateur in May 2009, he won The Irish Open on the European Tour, defeating Robert Rock on the third hole of a sudden death playoff. The win, on his tour début, made him just the third amateur to win on the European Tour, following Danny Lee earlier in the 2009 season, and Pablo Martín in 2007. Lowry shot a 62 to equal the lowest ever by an amateur on the circuit and led from the second round onwards.
Frys.com Open: At the Frys.com Open in Scottsdale, Ariz., reached a three-way playoff with Jamie Lovemark and eventual-winner Troy Matteson. Began the final round four strokes behind Matteson, but played his first five holes in 5-under, punctuated by a hole-in-one from 211 yards at the par-3 fifth hole. After finishing T2 in the playoff, he had recorded all eight of his professional rounds in the 60s. Thanks to the T7 in Las Vegas at the Justin Timberlake Shriners Hospitals for Children Open and T2 finish at Grayhawk GC, he surpassed No. 150 from the 2008 money list, earning special temporary membership on TOUR for the remainder of the season.
PGA Championship: With his T5 finish at the PGA Championship, finishing three strokes behind champion Justin Thomas, continued to be a top-five machine in major championships, recording his seventh such finish in 32 starts. Made a furious Sunday rally, with six birdies, including four in a row on Nos 12-15, but pars on The Green Mile (Nos. 16-18) left him a few short of his friend, Justin Thomas.
In May 2012, Fowler won the Wells Fargo Championship in Charlotte on the first extra hole of a sudden-death playoff. Replaying the 18th hole, he defeated Rory McIlroy and D. A. Points with a birdie to gain his first PGA Tour win. Fowler shot a 69 (−3) in the final round to finish in a three-way tie after 72 holes at Quail Hollow Club. This win enabled Fowler to break the top-25 in the world, placing him at number 24. The following week at The Players Championship in Ponte Vedra Beach, Florida, Fowler played the final hole at −11 under par and had a birdie opportunity to bring him within one of leader and eventual winner Matt Kuchar. Fowler, however, pushed his putt to the right and finished in a tie for second, the fifth second-place finish of his career.
Waste Management Phoenix Open: Claimed his second runner-up finish at the Waste Management Phoenix Open, one shot behind Hunter Mahan. Had birdie opportunities on the last three holes but unable to catch Mahan. Previously lost in a playoff to Troy Matteson just down the road at Grayhawk GC in the 2009 Frys.com Open. Had he won at TPC Scottsdale, would have become the first Sponsor Exemption to do so since Jason Gore (2005 84 Lumber Classic). Lee Westwood later won in June as a Sponsor Exemption at the St. Jude Classic presented by Smith & Nephew.
Abu Dhabi HSBC Golf Championship: Held off final-round charges from Thomas Pieters, Rory McIlroy and Henrik Stenson to win the Abu Dhabi HSBC Golf Championship, marking his second European Tour title. The victory was the first at the event by an American since Chris DiMarco won the inaugural event in 2006. Final-round highlights included a holed bunker shot on the eighth hole (which helped propel him to a three-stroke cushion at the turn), a chip-in for birdie on the 17th hole and then a par on the last to hold off Pieters by one stroke.
On June 3, 2018, DeChambeau won the Memorial Tournament in Dublin, Ohio, in a sudden-death playoff against Kyle Stanley and An Byeong-hun, after the three finished regulation play tied at −15. After Stanley bogeyed the first hole of sudden death, DeChambeau then proceeded to win with a birdie on the second hole, giving him his second win on the tour.
With this win, he entered the Official World Golf Ranking as an amateur at No. 168 and reached a career high of sixth in the World Amateur Golf Ranking. Walker Cup captain Colin Dagleish described the win as "fairytale stuff", adding: "You'd have to say that Shane's victory was the biggest (of the three amateur wins). To win your own national Open is quite something. It was unbelievable, it really was." The win was only the second home victory since 1982 and the first since Pádraig Harrington in 2007. Harrington himself was also full of praise: "It's fabulous for Irish golf. You only have to look at the fact it is such a rarity for an amateur to win, such a rarity for an Irish player to win the Irish Open. So, on a lot of fronts, it is a big deal. It was very impressive."
Lowry elected to turn professional the week after his Irish Open triumph, meaning that he would miss out on the opportunity to play in the Walker Cup in September 2009. He made his professional début on 28 May at the European Open, where he shot 78 in the first round to end the opening day almost at the back of the field, and went on to miss the cut following a second round 73.