In an Instagram post that shows Mayfield proposing to Wilkinson while on one knee, the 2018 No. 1 overall draft pick wrote, "Can't wait to do life with the most perfect girl. Emily Wilkinson, I love you."
The 23-year-old Mayfield is set to enter his first NFL season after an all-time great collegiate career at Oklahoma.
Last season, he won the Heisman Trophy and led the Sooners to the College Football Playoff.
Mayfield is currently behind veteran Tyrod Taylor in Cleveland's depth chart, but he was selected with an eye toward bringing the Browns back to prominence after a 0-16 campaign in 2017.
In May, TMZ Sports reported that Wilkinson was quitting her job as a patient coordinator at a plastic surgery center in Beverly Hills, California, to move to Cleveland with Mayfield.
At that time, TMZ noted that Mayfield and Wilkinson had been dating for "a couple of months."