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.
After Lowry's loan spell at Leeds was coming to an end, on 11 May he signed a new two-year contract extension at Aston Villa. It was a remarkable few days for Lowry, he was promoted with Leeds, received a call up to Australia's World Cup Squad and on the same day he signed a new two-year deal with Villa. Despite signing a contract with the club, Leeds United was considering re-signing him for the second time ahead of the 2010–11 season, but never happened.
Masters Tournament: Finished runner-up at the Masters, one stroke behind Patrick Reed, for his best result at the event. For the first time in eight starts at Augusta National, recorded four par-or-better rounds (70-72-65-67). Earned his third runner-up in a major (2nd/2018 Masters Tournament, T2/2014 The Open Championship, T2/2014 U.S. Open) and third top-five in the last four (2nd/2018 Masters Tournament, T5/2017 Open Championship, T5/2017 U.S. Open). With third-round 65, was one of just four players to post a bogey-free round during the week (Rory McIlroy/65, Jon Rahm/65, Si Woo Kim/65) with all four occurring in the final round.
At the first FedEx Cup playoff event of the season, The Barclays, Fowler went into the final round leading the event by one stroke. He endured a difficult final round, shooting a two-over-par 74. His challenge was ended with a double-bogey at the 16th hole that put him four strokes behind playing partner Patrick Reed. He went on to finish T7, three strokes behind the winner Reed. As a result of this, Fowler also failed to secure his automatic Ryder Cup spot, which he would have done with a top-three finish. Fowler moved up from 28th to 16th in the FedEx Cup standings with this result.
The Barclays: Held a one-stroke lead over Patrick Reed after 54 holes at The Barclays in the FedExCup Playoffs, before a double bogey-birdie-bogey finish on Nos. 16-18 resulted in a T7 at 6-under 278 with Jason Kokrak and Ryan Moore. Fowler went bogey free at Bethpage Black from the 10th hole in round one until the 11th hole in the final round, a span of 55 holes. His 55-consecutive holes without a bogey became a personal best on the PGA TOUR, besting 53 from the 2010 Memorial Tournament. This streak also marked the longest recorded in Barclays history since hole information began in 1983. Ian Poulter had the longest with 45 in 2010. The finish marked his third top-10 showing in his last four starts in the event (T9/2013, T9/2014).