In 1965, Naismith played the title role of the Virginia statesman George Mason in the NBC documentary series, Profiles in Courage. william Bakewell played George Wythe in the episode, and Arthur Franz was cast as James Madison. In 1965, Naismith guest-starred as barber Gilly Bright in episode 25, "The Threat" of the ABC military drama, 12 O-Clock High (TV series) and in the ABC action drama, The Fugitive, starring David Janssen. In 1969 he played Don Q Hought in an episode of Bonanza. He played Judge Fulton in the television series The Persuaders! (1971), with Tony Curtis and Roger Moore. He portrayed Emperor of Austria Franz Joseph in the BBC production Fall of Eagles (1974). Naismith played the Prince of Verona in the BBC Television Shakespeare version of Romeo and Juliet. He also appeared in the BBC sitcom Oh Father (1972).