He spent another season and a half with the Indians, then was traded to the Kansas City Royals on June 8, 1973, for Mike Jackson; the Royals had been particularly interested in acquiring Mingori since he was a Kansas City native. Mingori had 36 appearances in both 1974 and 1975, and had ERAs of 2.81 and 2.50. He followed that up with a 5–5 record and 2.32 ERA in 55 appearances in 1976.
He spent another season and a half with the Indians, then was traded to the Kansas City Royals on June 8, 1973, for Mike Jackson; the Royals were interested in acquiring him because he was from Kansas City. He made 36 appearances in both 1974 and 1975, posting ERAs of 2.81 and 2.50. He continued his success with a 5–5 record and 2.32 ERA in 55 appearances in 1976.