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.
In 2008, Fowler repeated as Sunnehanna Amateur champion. In the first round of the U.S. Open, Fowler shot a −1 (70) and was in a tie for 7th place. He was one of three amateurs to make the cut, along with Derek Fathauer and Michael Thompson. He ended the tournament tied for 60th. In October 2008 Fowler played on the Eisenhower Trophy team that finished second. He was the leading individual player.
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.