His film work affected his TV career: the reviews he received for his role as D.A. Fletcher in Dick Tracy led him to star as the character Dr. Mark Sloan first in an episode of Jake and the Fatman, then in a series of TV movies on CBS that became the foundation for his popular television drama Diagnosis: Murder. The series ran from 1993 to 2001 with son Barry Van Dyke co-starring in the role of Dr. Sloan's son Lieutenant Detective Steve Sloan. Also starring on the same show was daytime soap actress Victoria Rowell as Dr. Sloan's pathologist/medical partner, Dr. Amanda Bentley, and Charlie Schlatter in the role of Dr. Sloan's student, Dr. Jesse Travis. Van Dyke continued to find television work after the show ended, including a dramatically and critically successful performance of The Gin Game, produced for television in 2003 that reunited him with Mary Tyler Moore. In 2003, he portrayed a doctor on Scrubs. A 2004 special of The Dick Van Dyke Show titled The Dick Van Dyke Show Revisited was heavily promoted as the first new episode of the classic series to be shown in 38 years. Van Dyke and his surviving cast members recreated their roles; although nominated for a Primetime Emmy,[better source needed] the program was roundly panned by critics. In 2006 he guest-starred as college professor Dr. Jonathan Maxwell for a series of Murder 101 mystery films on the Hallmark Channel.
Van Dyke left high school in 1944, his senior year, intending to join the United States Army Air Forces for pilot training during World War II. Denied enlistment several times for being underweight, he was eventually accepted for service as a radio announcer before transferring to the Special Services and entertaining troops in the continental United States. He received his high school diploma in 2004 at the age of 78.