Nack-Hoi, 56, formerly Cheil's executive vice-president for client services, replaces Dong-Man Bai, who is stepping down after six years.
Nack-Hoi has worked for Cheil since leaving university in 1976. He has helped translate several books on advertising and marketing into the Korean language, and holds a civil merit award from the South Korean government for his services to the advertising industry.
Dong-Man becomes president of the Samsung social contribution committee, which funds initiatives on behalf of disabled people. Samsung is Cheil's biggest client.