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.
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.
Lowry missed the first three cuts of his professional career, but had his first payday on 5 July, when he finished 50th at the Open de France ALSTOM. He had his best professional result in November 2009, when he finished 3rd in the Dunlop Phoenix Tournament in Japan. In January 2010, Lowry finished in fourth place in the Abu Dhabi Golf Championship, moving him into the top-100 of the Official World Golf Ranking.
Waste Management Phoenix Open: Won fifth PGA TOUR title at the Waste Management Phoenix Open in his 220th career start at the age of 30 years, 1 month, 21 days. Began the final round with a four-shot lead and won by two strokes after recording a double bogey and triple bogey en route to a closing 3-over 74. Became the first player since 1983 to win with both a double bogey and triple bogey or worse in the final round. Triple bogey came at No. 11 at TPC Scottsdale after he chipped his ball into the water and received an additional penalty when the ball rolled back into the water after he had placed it back into play. Marked the second time of seven occasions he converted a 54-hole lead to victory.
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.
On 23 November 2011, Lowry was again loaned out to play in the Championship, this time to Millwall until 3 January 2012. He followed Aston Villa team-mate Nathan Baker who also signed on loan for Millwall two days earlier. Lowry made his Millwall debut three days later, where he played 90 minutes, in a 0–0 draw against Crystal Palace. His impressive display at Millwall soon earned a loan extension. Weeks later on 13 January 2012, Lowry was sent-off in the 22nd minutes after stamping on Nikola Žigić, which saw Millwall lose 6–0. Three years on after signing for Birmingham City, Lowry stated, quoting: "Whatever club I play for I fully commit to that club at the time. I play with my heart on my sleeve. Sometimes in the past I have gone overboard but I was a younger player then, I have learned a lot from these types of experiences. But I am an aggressive player, that’s the way I like to play and I can’t change the way I play. I will use my experience now and be a bit more clever."'
Enjoyed a stellar rookie season, with seven top-10 finishes and a 32nd-place finish in the FedExCup standings that led to him winning PGA TOUR Rookie of the Year honors. Finished inside the top 30 on the money list to qualify for the Masters and the U.S. Open. Played in first three Playoff events, slipping from 21st to 32nd and out of the TOUR Championship.
On 27 January 2016, Lowry returned to Australia after a decade away from Australia when he signed a two-and-a-half-year deal with A-League side Perth Glory. Upon joining Perth Glory, Lowry said of the move, quoting: "I've got a lot of experience behind me now and I want to use it to guide the young lads who are in this young squad. I've spent 11 years in England and it's shaped my football over there and I'm really happy to be here and get stuck into the games"