Donald James Yarmy was born in New York City and served with the USMC during World War II, being invalided out with malaria during the battle of Guadalcanal. He worked as a comic and mimic, taking the stage-name of Adams. His work on television began in 1954. After the success of Get Smart his later efforts were less successful, including three attempts to revive the Get Smart series in the 1980s. He continued to make the majority of his income from live work on stage and in clubs.
Adams won three Emmy Awards for his portrayal of Max, an Emmy record that was broken by Carroll O'Connor and tied by Kelsey Grammer. After Get Smart, Adams did the comedy series The Partners.
He also works as a voice actor. His first work was in Tennessee Tuxedo and his Tales (1963-1966), but he is more famous as the voice of Inspector Gadget, both in the initial television series (1983-1985) and in later reprises.
He has been married three times and has six(?) children.