Deutsche Bank Championship: Shot a final-round 3-under 68 to come from one shot back and defeat third-round leader Henrik Stenson at the Deutsche Bank Championship, good for his third career PGA TOUR victory. Earned the win at age 26 years, 8 months, 25 days in his 150th career start. Collected 2,000 points and moved from No. 22 to No. 3 in the FedExCup standings. Has come from behind to win all three of his PGA TOUR events, with his first two wins via playoffs (2012 Wells Fargo Championship and 2015 PLAYERS Championship). Became the sixth consecutive come-from-behind winner at TPC Boston.
Though he appeared in two matches as an un-used substitute for Aston Villa in the 2010–11 season, Lowry continued to be remain out of the first team and in January 2011, Lowry signed for Championship side Sheffield United until the end of the season making his first start for the Blades away at Coventry City a day later. Lowry made eighteen appearances for the Blades but with the club in decline he was unable to prevent them from being relegated at the end of the season.
Wells Fargo Championship: Made birdie-3 on the first extra hole (No. 18) to defeat Rory McIlroy and D.A. Points at the Wells Fargo Championship for his first TOUR win. Improved to 1-1 in playoffs (lost to Troy Matteson, 2009 Frys.com Open). The playoff was the fifth at the Wells Fargo Championship. At the age of 23 years, 4 months, 23 days, became the third player to make the Wells Fargo Championship his first PGA TOUR win (Anthony Kim in 2008 and McIlroy in 2010). Became the third-youngest winner of the event, behind McIlroy (20 years, 11 months, 28 days) and Kim (22, 10, 15). His win came in his 72nd start on TOUR and was his 16th top-10 finish. Opening-round 66 is the lowest start by a winner of the Wells Fargo Championship. Won in his third start at the Wells Fargo Championship (T6 in 2010 and T16 in 2011).
Lowry made his professional debut in the 2009–10 UEFA Europa League in an away fixture at Rapid Vienna. On 17 September 2009, Lowry signed a three-month loan deal with Football League Championship side Plymouth Argyle. Lowry made his Plymouth Argyle debut on 19 September 2009, playing 90 minutes, in a 3–1 loss against Newcastle United. He played 13 league games for Plymouth during his loan spell, where he impressed many and was recalled by Villa who required Lowry's services as cover after some injuries to defenders.
Kolon Korea Open: Won his first tournament as a professional, the Kolon Korea Open on the OneAsia Tour, when he rolled to a six-stroke win over Rory McIlroy at Woo Jeong Hills CC in early October. He took control of the tournament in the third round when he shot an 8-under 63. He followed that with a 3-under 68 Sunday. The victory was worth a little under $250,000.
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.