The Twilight star and her husband, singer Paul McDonald, took part in the Rock 'n' Roll Las Vegas challenge and completed the race in just under two and a half hours.
The couple raised money for The Crohn's & Colitis Foundation of America (CCFA), and McDonald is delighted with their finishing time.
In a post on his Twitter.com page, he writes, ""We made it! Our first half marathon! 13.1 miles in 2 hrs 25 min 18 seconds! Woohoo!""