On December 18, 2014, he signed a two-year deal (with a mutual option for a third year) with the Kansas City Royals for a guaranteed $8.5 million.
He started the 2015 season on the 60-day disabled list to continue recovering from his second Tommy John surgery and made his first appearance for the Royals on July 20, 2015 against the Pirates.
He made his first start for the Royals on Monday, August 24, 2015, against the Baltimore Orioles.
He made 15 appearances (8 starts) in 2015 with a 6–2 record and a 4.01 ERA.
He was also part of the Royals postseason run as the team won the 2015 World Series over the New York Mets, their first championship in 30 years.

On May 12, 2016, Medlen was placed on the 15-day disabled list due to right rotator cuff inflammation.
The Royals declined Medlen's 2017 option on November 4, making him a free agent.
On December 18, 2014, he signed a two-year deal (with a mutual option for a third year) with the Kansas City Royals for a guaranteed $8.5 million. He started the 2015 season on the 60-day disabled list to continue recovering from his second Tommy John surgery and made his first appearance for the Royals on July 20, 2015 against the Pirates. He made his first start for the Royals on Monday, August 24, 2015, against the Baltimore Orioles. He made 15 appearances (8 starts) in 2015 with a 6–2 record and a 4.01 ERA. He was also part of the Royals postseason run as the team won the 2015 World Series over the New York Mets, their first championship in 30 years.
On May 12, 2016, Medlen was placed on the 15-day disabled list due to right rotator cuff inflammation. The Royals declined Medlen's 2017 option on November 4, making him a free agent.
Kris Medlen