In May 2010, he became the youngest Australian to win a PGA Tour event, winning the HP Byron Nelson Championship. Day gained entry into his first ever major championship at the 2010 Open Championship after Greg Norman withdrew. Day went on to make the cut and finish in a tie for 60th place. In August 2010, Day made his first appearance at the PGA Championship, where a 66 on Saturday helped him to finish seven-under-par for the tournament and earn his first top-10 in a major. This run of form continued during the FedEx Cup playoff season, where Day enjoyed top-five finishes at the first two playoff events to qualify for the season-ending Tour Championship. He would go on to finish T17 at East Lake Golf Club and ended the 2010 season ranked 21st on the PGA Tour money list.