John Byner's voice work includes the long-running cartoon series The Ant and the Aardvark, in which the title characters are voiced by Byner's dead-on impressions of Dean Martin and Jackie Mason, respectively.

On The Ed Sullivan Show, where he made his first early TV appearances, he mimicked Ed Sullivan as well as anyone, including the "master" Sullivan impersonator, Will Jordan. His other impressions included John Wayne, and he even sang as Dean Martin.

On a 1967 episode of Get Smart, Byner played a KAOS agent who made a phone call to the Chief of CONTROL (played by Edward Platt), performed a perfect impression of President Lyndon B. Johnson, and told the Chief he was fired and replaced with agent Maxwell Smart (Don Adams). Smart, the Chief and Agent 99 (Barbara Feldon) foiled this plot to undermine CONTROL, and Byner's character was arrested.

In the late 1970s, he had a featured role as Detective Donahue on the tv series Soap.

In the 1980s he hosted the Canadian TV comedy series, Bizarre. That show introduced many people to hapless daredevil Super Dave Osborne, played by Bob Einstein. His popularity on Bizarre led to his own spin-off variety show, cartoon series, and movie.

Over the years he has done straight acting work and also light characters in otherwise serious dramas, such as "Cotton Dunn" in the 1990s cop series Silk Stalkings.