The first season of The Twilight Zone aired Fridays at 10:00–10:30 pm on CBS from October 2, 1959 to July 1, 1960. There are 36 episodes, including the pilot, "Where Is Everybody?". The theme music for this season, written by Bernard Herrman, is different from the music most commonly associated with the series, written by Marius Constant for the second season onwards.

The second season of The Twilight Zone aired Fridays at 10:00–10:30 pm on CBS from September 30, 1960 to June 2, 1961. There are 29 episodes.

The third season of The Twilight Zone aired Fridays at 10:00–10:30 pm on CBS from September 15, 1961 to June 1, 1962. There are 37 episodes. Continuing with Marius Constant's theme music, a different set of graphics was used for the opening, consisting of a rotating cone with concentric circles suggesting a spiral, receding into a star field. Rod Serling's narration from the second season was used, with the verse "That's the signpost up ahead" taken out: "You're traveling through another dimension. A dimension not only of sight and sound but of mind. A journey into a wondrous land whose boundaries are that of imagination. Your next stop—The Twilight Zone." Some subtle changes in the opening's acoustics were made beginning with Person or Persons Unknown.

The fourth season of The Twilight Zone aired Thursdays at 9:00–10:00 pm on CBS from January 3 to May 23, 1963. This season broke with the previous seasons in presenting hour-long episodes instead of the earlier half-hour episodes. A very different and more complex set of graphics was used for the intro, and Rod Serling's narration changed from the earlier seasons as well: "You unlock this door with the key of imagination. Beyond it is another dimension. A dimension of sound. A dimension of sight. A dimension of mind. You're moving into a land of both shadow and substance, of things and ideas. You've just crossed over into the Twilight Zone."

The fifth and final season of The Twilight Zone aired Fridays at 9:30–10:00 pm on CBS from September 27, 1963 to June 19, 1964. It featured the same intro as the fourth season, but reverted to the original half-hour format.