[2] In the 1983 MLB draft, the California Angels selected Joyner in the third round as a compensation pick from the New York Yankees for signing Don Baylor.

Joyner credited a stint with the Mayagüez Indians of the Puerto Rican Professional Baseball League as fundamental in his improvement as a slugger.

[2] Then-batting coach José Manuel Morales forced him to do power weight training and modify his posture at the batting cage, so as to develop upper body strength.

[3] He was consequently the top hitter on Puerto Rico's winter league on the 1985–86 season, winning the Triple Crown (.356, 14 HR, 48 RBI) in 54 games.

[2] During his rookie season with the California Angels, Joyner became a fan favorite and briefly inspired a sensation in which Anaheim Stadium was dubbed "Wally World", after the fictional theme park in the film National Lampoon's Vacation.

Against the Texas Rangers on June 16, he foiled Charlie Hough's bid with a single with one out in the ninth, scoring Jack Howell (who had reached on a three-base error) to tie the game at 1–1.

In a taped message that was played on the Edison Field videoboard after the first inning that day, he thanked the Angels fans for their support and received a standing ovation.

[11] Joyner told Buster Olney that his reason for telling his story in public was to set the record straight for the sake of his daughters.

On July 31, 2007, Joyner was hired by the San Diego Padres to be their hitting coach, replacing Merv Rettenmund.

In spite of this, Joyner was likely to be let go at the end of the year like Bench Coach Craig Colbert was on September 29, 2008, due to the same factors in his resignation.

Joyner has invested in and appeared in films marketed to members of the Church of Jesus Christ of Latter-day Saints, including playing "Brother Angel" (a reference to the California Angels) in The Singles Ward, and "Brother Jensen" in the 2003 movie, The R.M..[18][19] He is the nephew of former United States Senator Paula Hawkins.