He gained worldwide fame and became a cultural icon for his portrayal of James T. Kirk, captain of the USS Enterprise, in the science fiction television series Star Trek from 1966 to 1969, Star Trek: The Animated Series and in seven of the subsequent Star Trek feature films.
From 2004 to 2008, he starred as attorney Denny Crane in over 100 episodes of the television dramas The Practice and its spin-off Boston Legal, for which he has won two Emmy Awards and a Golden Globe Award.