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.
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.
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.
THE PLAYERS Championship: A week after collecting his first PGA TOUR victory, nearly became the first player since David Duval (1997) to post first two TOUR victories in back-to-back weeks, finishing T2 at THE PLAYERS, two strokes behind winner Matt Kuchar. Holed a birdie attempt from 21 feet, 7 inches on the par 3 17th in the final round to move to 11-under but couldn't convert a 7-foot, 7-inch birdie on No. 18 that would have given him the clubhouse lead at 12-under. Recorded his fifth career runner-up finish on TOUR in his 73rd start. His T2 performance came in his third start at THE PLAYERS and first in which he made the 36-hole cut. Moved into contention with a 66 in the third round, a career low at TPC Sawgrass. Entered the final round three shots off the 54-hole pace.
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."
All of DeChambeau's irons and wedges are cut to exactly the same length: 37.5 inches (95.3 cm). Their lie and bounce angle are also the same; only the lofts are different. In addition to the single-length concept, his clubs are unusual for their extremely upright lie angle.  DeChambeau keeps the club on the same plane throughout his swing and does not turn his wrists during his swing. In 2011, at the suggestion of his instructor Mike Schy, DeChambeau switched to JumboMax Grips, the largest grips commercially available. The larger grips allow DeChambeau to hold the grips in his palms and not his fingers.
Hyundai Tournament of Champions: Finished T6 in a Monday-start-Tuesday-finish event, the season-opening, 54-hole Hyundai Tournament of Champions. The event "started" twice during the regularly scheduled first round Friday and later Sunday, but both times PGA TOUR rules staff halted play due to unplayable windy conditions and subsequently voided all scores that had taken place. As the first player off the tee, he ended up hitting three "opening" shots of the season.