K
- Byron Kane ("From Agnes—With Love") (uncredited)
- Richard Karlan ("Execution" and "The Mirror")
- Doris Karnes ("What You Need" and "The Lateness of the Hour")
- Robert Karnes ("The Arrival")
- Carolyn Kearney ("Ninety Years Without Slumbering")
- Buster Keaton ("Once Upon a Time")
- Don Keefer ("It's a Good Life", "From Agnes—With Love", and "Passage on the Lady Anne")
- Noah Keen ("The Arrival" (as Noah Keene) and "The Trade-Ins")
- Valley Keene ("The Lateness of the Hour")
- William Keene ("The Prime Mover" and "The Midnight Sun")
- Michael Keep ("Person or Persons Unknown")
- Robert Keith ("The Masks")
- Cecil Kellaway ("Elegy" and "Passage on the Lady Anne")
- Mike Kellin ("The Thirty-Fathom Grave")
- Robert Kelljan ("The Jeopardy Room")
- Ray Kellogg ("A Kind of a Stopwatch") (credited as Ray Kellog)
- Don Kelly ("The Mighty Casey") (as Don O'Kelly)
- Ricky Kelman ("Young Man's Fancy")
- Pert Kelton ("Miniature")
- Ed Kemmer ("Nightmare at 20,000 Feet")
- Warren J. Kemmerling ("The Passersby")
- Kenner G. Kemp ("To Serve Man" (uncredited) and "The Silence") (uncredited))
- Doris Kemper ("Printer's Devil")
- William Kendis ("Will the Real Martian Please Stand Up?" and "The Fever")
- Madge Kennedy ("On Thursday We Leave for Home")
- Jack Kenny ("The Night of the Meek") (uncredited)
- Dennis Kerlee ("The Changing of the Guard")
- George Keymas ("The Eye of the Beholder")
- Sandy Kenyon ("The Odyssey of Flight 33", "The Shelter" and "Valley of the Shadow")
- Richard Kiel ("To Serve Man")
- Wright King ("Shadow Play" and "Of Late I Think of Cliffordville")
- Lenore Kingston ("It's a Good Life")
- Ron Kipling ("Will the Real Martian Please Stand Up?")
- Lee Kinsolving ("Black Leather Jackets")
- Phyllis Kirk ("A World of His Own")
- Helen Kleeb ("Jess-Belle")
- Robert Kline ("Showdown with Rance McGrew")
- Jack Klugman ("A Passage for Trumpet", "A Game of Pool", "Death Ship" and "In Praise of Pip")
- Ted Knight ("The Lonely") (uncredited)
- Gail Kobe ("A World of Difference", "In His Image" and "The Self-Improvement of Salvadore Ross")
- Kenneth Konopka ("Caesar and Me") (uncredited)
- John Kroger ("The Trouble With Templeton") (uncredited)
- Fred Kruger ("What You Need" "Back There" (uncredited))
- Charles Kuenstle ("The Thirty-Fathom Grave")
- Daniel Kulick ("Cavender Is Coming" and "On Thursday We Leave for Home")
- Nancy Kulp ("The Fugitive")
- Will Kuluva ("The Mirror" and "The New Exhibit")
Read more about this topic: List Of The Twilight Zone (1959 TV Series) Guest Stars