Born Walter Matthow on October 1, 1920, to a pair of Russian-Jewish immigrants in New York City, Matthau grew up poor on the Lower East Side and started out selling soft drinks and playing bit parts at a Yiddish theater at age 11. He was paid 50 cents for each of his occasional onstage appearances. His father, a peddler from Kiev, left home when he was 3 years old. He lived with his older brother, Henry, and their mother, a garment worker, on the Lower East Side of New York. After graduating from Seward Park High School during the Depression, he took government jobs as a forester in Montana, a gym instructor for the Works Progress Administration and a boxing coach for policemen. During World War II, he served in the Army Air Corps as a radio cryptographer in a heavy bomber unit in Europe and returned home a sergeant with six battle stars.

In 1948, his first Broadway role was when he was hired as an understudy for the role of an 83 year old English bishop in 'Anne of the Thousand Days' starring Rex Harrison. His fame came with The Fortune Cookie and The Odd Couple. While making the former, he suffered a serious heart attack. This was due to heavy smoking and chronic gambling. In 1976, he had heart bypass surgery. In 1993, he was hospitalized for double pneumonia. In 1995, he had a benign colon tumor removed. In 1999, he was hospitalized again for pneumonia. His ill health was due to his eating habits. He had two children with Grace Johnson, David and Jenny.
Big break came when understudying the actor who played the Archbishop in "Anne Of The Thousand Days", starring Rex Harrison. Brought to the St. John's Health Center after suffering a heart attack by ambulance and was pronounced dead shortly afterward at 1:42 a.m. Buried at Pierce Brothers Westwood Village Memorial Park. Marilyn Monroe, Truman Capote, Natalie Wood, Donna Reed, among other stars are buried at this cemetery. People were never sure if he was joking or saying things seriously, either on-screen or out-screen. He hated to be identified as a comedic actor. He once claimed that his father was an Orthodox priest in the Czarist Russia, who was removed after he claimed that the Pope was infalible. Once claimed that his wife's name was Carol Wellington-Smythe Marcus, just to give it a more "aristocratic" sound. When he inscribed himself formally to the U.S. Social Security in 1937, he included "Foghorn" as his middle name. He never changed it. Studied in the dramatic workshop at New York's New School with Gene Saks, Rod Steiger, Harry Guardino and Tony Curtis. Served in the Army Air Corps with James Stewart He once estimated his lifetime gambling losses at $5 million. While making a TV series in Florida before his movie stardom, he lost $183,000 betting on spring-training baseball games. After filming "Grumpy Old Men" in 1993 in freezing weather in Minnesota, he was hospitalized for double pneumonia. Uncle of Juliette Gruber. Reports are that he made up "Matuschanskayasky" as a joke and that his real "real" name is Matthow. The existence of Michelle Matthow would seem to confirm this... According to his son, Charlie Matthau, on Larry King Live, July 14, 2000, his real name was Walter Matthow, and he changed it to be more exotic. The name Walter Matuschanskayasky was one he made up to retaliate for being "tricked" into appearing in the movie Earthquake with a much larger part than he expected. Was passionate about classical music and often sang pieces by Mozart on the set. Two children, Jenny (b. 2 August 1956) and David (b. 2 November 1953), by his first wife, Grace Geraldine Johnson, and a son, Charles Matthau (b. 10 December 1962), by his second wife, Carol Marcus. Step-father of Lucy Saroyan Very tall as young man, Matthau had a very slouchy posture by the time he was an actor. This was in part due to injuries attained in combat in WWII, but he probably exaggerated it because the slouch fitted his miserly characters. 'Dan Castelleneta' has said that his original voice for Homer Simpson was simply an impression of Matthau. Won two Tony Awards: in 1962, as Best Supporting or Featured Actor (Dramatic) for "A Shot in the Dark," and in 1965 as Best Actor (Dramatic) for "The Odd Couple," recreating his part as Oscar Madison in the film version of the same name, The Odd Couple. Previously, he also had a Tony nomination in 1959 as Best Supporting or Featured Actor (Dramatic) for "Once More, with Feeling." Dealt with a gambling addiction his entire adult life. He and Jack Lemmon acted together in 10 movies: Buddy Buddy, The Fortune Cookie, The Front Page, The Grass Harp, Grumpier Old Men, Grumpy Old Men, JFK, The Odd Couple II, The Odd Couple and Out to Sea. Lemmon also directed Matthau in Kotch.