The CMA announced the selections Wednesday in Nashville. All three will be formally inducted in a ceremony this spring.
Mandrell's hits include "Sleeping Single in a Double Bed" and "I Was Country When Country Wasn't Cool."
McCoy was chosen for his skill as a musician, especially on harmonica. He was one of Nashville's top session players in the 1960s and '70s.
Inductees are chosen by more than 300 voters appointed by the CMA's board of directors.