In 1973, Geary made his daytime television debut in the short-lived role of George Curtis on The Young and the Restless, and exited the series later that year.
In November 1978, Geary debuted on General Hospital in the role of Luke Spencer. His character began as a "hit man" and later as a rapist who fell in love with, and subsequently married, his victim, Laura Webber (portrayed by Genie Francis). Due to the character's immense popularity, the writers turned Luke into one of the series' leading protagonists. With the November 17, 1981 wedding of Luke and Laura, one of General Hospital's greatest love affairs in the history of the series began. The early 1980s saw Luke becoming involved in a series of nearly improbable storylines, seemingly lifted from the pages of a spy novel, which only served to increase the popularity of the character. Geary left the series in 1984.
In 1991, Geary returned to General Hospital in a new role as Bill Eckert, the look-a-like cousin of Luke. After two years in the role, the character of Bill was killed off, and Geary set about reprising his role as Luke in October 1993.