Swartz is in his 33rd year in the Kansas City organization. He's been with the Royals for 21 years and spent the last 19 as the head trainer.
"It's been a great run and something I have been blessed with the good fortune of doing what I aspired to do from the first day I entered college, but I realized in the last few weeks that it was time for me to step away," Swartz said in a statement.
He thanked the Royals organization and the players and managers that he served.
"It's time for me to spend some time at home and enjoy life outside the game," he said.
Swartz joined the organization in 1977 and served at Sarasota, Fort Myers, Jacksonville and Omaha before joining the Major League club. In 1996 and 2006, he was the trainer for the American League All-Star team.
"Nick approached us several weeks ago about this possibility but I back-burnered it in hopes that he would reconsider the request," Royals general manager Dayton Moore said. "When the club came home from its most recent road trip, Nick remained steadfast in his decision and we will honor his wish. Nick has dedicated his entire adult life to the well being of professional baseball players, both in the treatment of injuries and injury prevention, and has been a tremendous asset to this organization and the game of baseball."
Swartz and his wife CeeCee live in Blue Springs, Mo.