Piers Morgan, a British talk-show host and "America's Got Talent" judge, will take over the 9 p.m. Eastern time slot in January.
King has conducted thousands of interviews over his broadcasting career. He joined CNN in 1985 and has recorded more than 6,000 shows for the network.
Rival cable station MSNBC saluted King by buying an ad in USA Today on Thursday, calling King "one of a kind."
The Associated Press contributed to this report.