Walter Koenig was born in Chicago, Illinois in September 4, 1936. Shortly thereafter, his parents moved to the Inwood area of Manhattan where he and his brother grew up. His first ever acting experience was in a stage, performing at the Fieldston High School in New York playing the title role of "Peer Gynt". His next role was in the same venue in "The Devil's Disciple".

During summer, Koenig was involved with upstate New York's camps for underprivileged children. Koenig introduced a theatre program which is still in effect today that is played by disturbed and overly aggressive youngsters as therapy. He was a high school student when he devised this concept.

Koenig also took two years of pre-med courses at Grinell College in Iowa, thanks to his interest in psychiatry. He performed summer stocks during the summers. Walter and his family moved to California and transferred to UCLA where obtained a B.A. in pyschology. His father died when the family made the move.

Koenig's first TV role was a guest spot on "Day In Court". Some of his other credits includes, "Mr. Novak", "Gidget", "Jerrico", "The Lieutenant", "Ironside", "Mannix", "Medical Center", "The Untouchables", and "I, Spy". Other than his "Star Trek" roles for his portrayal of Ensign Chekov, his other noted roles was in an hour episode of Alfred Hitchcok Presents which was written by Harlan Ellison. Here he played a gang leader who discovers that an author, who has run with the gang for six weeks to get material for his book, has written about him.

In 1967, Koenig auditioned for a role on "Star Trek", which was to appeal to the 'younger generation'. Joining the cast during the second season, he appeared on a week-to-week basis which eventually became full-time. When George Takei took a ten-week leave of absence to work on a film, Koenig was getting his scenes.

Koenig also wrote two books, "Chekov's Enterprise", and "Buck Alice and The Actor Robot". His other writing credits include an episode for "Land Of The Lost" and "The Infinite Vulcan" for the animated "Star Trek" series. He also wrote an episode for "Powers of Matthew Starr", "Family" and "Class of '65".

After "Star Trek's" cancellation, Koenig began to make guest appearances on TV. He had a role in a Columbo with Bill Shatner and in the TV movie "Goodbye Raggedy Ann". His also appeared in another Roddenberry project called "The Questor Tapes" and Harlan Ellison's syndicated series, "The Starlost", which offered Koenig a recurring role as a villain.

Koenig's film opportunity came when he was cast in a movie called "Moontrap", where he met his wife Judy Levitt. Their sons and daughters also have taken up their parents acting trade and soon Andrew Koenig would have a recurring role on "Growing Pains" and Danielle Koenig would appear in two episodes of "Life Goes On" and on the short-lived series "The Fanelli Boys".

Koenig also toured with Mark Lenard, who portrays Sarek on "Star Trek" in the Bernard Sabbath play, "The Boys of Autumn".