Registered his first major title in August 2016 when he held off then-world No. 1 Jason Day to claim the PGA Championship at Baltusrol Golf Club in Springfield, N.J. It gave Walker 10 career victories, six of which have come on the PGA Tour. Recruited to Baylor University by 1989 U.S. Amateur Public Links champion Tim Hobby. Met wife, Erin, while she was serving as a volunteer during a 2004 Web.com Tour event. Member of the 2014 and 2016 USA Ryder Cup and 2015 Presidents Cup teams.
U.S. Open Record
| Year | Site | Scores | To Par | Finish |
| 2018 | Shinnecock Hills Golf Club | 75-70-79-73--297 | +17 | T-56 |
| 2017 | Erin Hills | 77-73 | +6 | MC |
| 2016 | Oakmont Country Club | 75-76 | +11 | MC |
| 2015 | Chambers Bay | 72-73-72-75--292 | +12 | T-58 |
| 2014 | Pinehurst Resort & C.C. (Course No. 2) | 70-72-71-69--282 | +2 | T-9 |
| 2002 | Bethpage State Park (Black Course) | 77-76 | +13 | MC |
| 2001 | Southern Hills Country Club | 79-66-74-73--292 | +12 | T-52 |