Matthau was trained in acting at the Dramatic Workshop of The New School with German director Erwin Piscator.
He often joked that his best early review came in a play where he posed as a derelict.
One reviewer said, "The others just looked like actors in make-up, Walter Matthau really looks like a skid row bum!"
Matthau was a respected stage actor for years in such fare as Will Success Spoil Rock Hunter?
and A Shot in the Dark.
He won the 1962 Tony Award for Best Featured Actor in a play.

Matthau appeared in the pilot of Mister Peepers (1952) with Wally Cox.
For reasons unknown he used the name Leonard Elliot.
His role was of the gym teacher Mr. Wall.
He made his motion picture debut as a whip-wielding bad guy in The Kentuckian (1955) opposite Burt Lancaster.
He played a villain in King Creole (1958), in which he gets beaten up by Elvis Presley.
Around the same time, he made Ride a Crooked Trail with Audie Murphy, and Onionhead (both 1958) starring Andy Griffith; the latter was a flop.
Matthau had a featured role opposite Griffith in the well received drama A Face in the Crowd (1957), directed by Elia Kazan.
Matthau also directed a low-budget movie called The Gangster Story (1960) and was a sympathetic sheriff in Lonely Are the Brave (1962), which starred Kirk Douglas.
He appeared opposite Audrey Hepburn in Charade (1963).

Appearances on television were common too, including two on Naked City, four installments of Alfred Hitchcock Presents, as well as an episode of The Eleventh Hour ("A Tumble from a Tall White House", 1963).
He appeared eight times between 1962 and 1964 on The DuPont Show of the Week and as Franklin Gaer in an episode of Dr. Kildare ("Man Is a Rock", 1964).
Additionally he featured in the syndicated crime drama Tallahassee 7000, as a Florida-based state police investigator (1961–62).

Comedies were rare in Matthau's work at that time.
He was cast in a number of stark dramas, such as Fail Safe (1964), in which he portrayed Pentagon adviser Dr. Groeteschele, who urges an all-out nuclear attack on the Soviet Union in response to an accidental transmission of an attack signal to U.S. Air Force bombers.
Neil Simon cast him in the play The Odd Couple in 1965, with Matthau playing slovenly sportswriter Oscar Madison, opposite Art Carney as Felix Ungar.
Matthau later reprised the role in the film version, with Jack Lemmon as Felix Ungar.
He played detective Ted Casselle in the Hitchcockian thriller Mirage (1965), directed by Edward Dmytryk.

He achieved great success in the comedy film, The Fortune Cookie (1966), as a shyster lawyer, William H. "Whiplash Willie" Gingrich, starring opposite Lemmon; the first of many collaborations with Billy Wilder, and a role that would earn him an Oscar for Best Supporting Actor.
Filming had to be placed on a five-month hiatus after Matthau had a serious heart attack.
He gave up his three pack a day smoking habit as a result.
Matthau appeared during the Oscar telecast shortly after having been injured in a bicycle accident; nonetheless, he scolded actors who had not attended the ceremony, especially the other major award winners that night: Paul Scofield, Elizabeth Taylor and Sandy Dennis.


Oscar nominations would come Matthau's way again for Kotch (1971), directed by Lemmon, and The Sunshine Boys (1975), another adaptation of a Neil Simon stage play, this time about a pair of former vaudeville stars.
For the latter role he won a Golden Globe award for Best Actor in a Musical or Comedy.

Broadway hits turned into films continued to cast Matthau in lead roles in Hello, Dolly!
and Cactus Flower (both 1969); for the latter film, Goldie Hawn received an Oscar for Best Supporting Actress.
Matthau played three roles in the film version of Simon's Plaza Suite (1971) and was in the cast of its followup California Suite (1978).

Matthau starred in three crime dramas in the mid-1970s, as a detective investigating a mass murder on a bus in The Laughing Policeman (1973), as a bank robber on the run from the Mafia and the law in Charley Varrick (also 1973) and as a New York transit cop in the
Matthau was trained in acting at the Dramatic Workshop of The New School with German director Erwin Piscator. He often joked that his best early review came in a play where he posed as a derelict. One reviewer said, "The others just looked like actors in make-up, Walter Matthau really looks like a skid row bum!" Matthau was a respected stage actor for years in such fare as Will Success Spoil Rock Hunter? and A Shot in the Dark. He won the 1962 Tony Award for Best Featured Actor in a play.
Matthau appeared in the pilot of Mister Peepers (1952) with Wally Cox. For reasons unknown he used the name Leonard Elliot. His role was of the gym teacher Mr. Wall. He made his motion picture debut as a whip-wielding bad guy in The Kentuckian (1955) opposite Burt Lancaster. He played a villain in King Creole (1958), in which he gets beaten up by Elvis Presley. Around the same time, he made Ride a Crooked Trail with Audie Murphy, and Onionhead (both 1958) starring Andy Griffith; the latter was a flop. Matthau had a featured role opposite Griffith in the well received drama A Face in the Crowd (1957), directed by Elia Kazan. Matthau also directed a low-budget movie called The Gangster Story (1960) and was a sympathetic sheriff in Lonely Are the Brave (1962), which starred Kirk Douglas. He appeared opposite Audrey Hepburn in Charade (1963).
Appearances on television were common too, including two on Naked City, four installments of Alfred Hitchcock Presents, as well as an episode of The Eleventh Hour ("A Tumble from a Tall White House", 1963). He appeared eight times between 1962 and 1964 on The DuPont Show of the Week and as Franklin Gaer in an episode of Dr. Kildare ("Man Is a Rock", 1964). Additionally he featured in the syndicated crime drama Tallahassee 7000, as a Florida-based state police investigator (1961–62).
Comedies were rare in Matthau's work at that time. He was cast in a number of stark dramas, such as Fail Safe (1964), in which he portrayed Pentagon adviser Dr. Groeteschele, who urges an all-out nuclear attack on the Soviet Union in response to an accidental transmission of an attack signal to U.S. Air Force bombers. Neil Simon cast him in the play The Odd Couple in 1965, with Matthau playing slovenly sportswriter Oscar Madison, opposite Art Carney as Felix Ungar. Matthau later reprised the role in the film version, with Jack Lemmon as Felix Ungar. He played detective Ted Casselle in the Hitchcockian thriller Mirage (1965), directed by Edward Dmytryk.
He achieved great success in the comedy film, The Fortune Cookie (1966), as a shyster lawyer, William H. "Whiplash Willie" Gingrich, starring opposite Lemmon; the first of many collaborations with Billy Wilder, and a role that would earn him an Oscar for Best Supporting Actor. Filming had to be placed on a five-month hiatus after Matthau had a serious heart attack. He gave up his three pack a day smoking habit as a result. Matthau appeared during the Oscar telecast shortly after having been injured in a bicycle accident; nonetheless, he scolded actors who had not attended the ceremony, especially the other major award winners that night: Paul Scofield, Elizabeth Taylor and Sandy Dennis.

Oscar nominations would come Matthau's way again for Kotch (1971), directed by Lemmon, and The Sunshine Boys (1975), another adaptation of a Neil Simon stage play, this time about a pair of former vaudeville stars. For the latter role he won a Golden Globe award for Best Actor in a Musical or Comedy. 
Broadway hits turned into films continued to cast Matthau in lead roles in Hello, Dolly! and Cactus Flower (both 1969); for the latter film, Goldie Hawn received an Oscar for Best Supporting Actress. Matthau played three roles in the film version of Simon's Plaza Suite (1971) and was in the cast of its followup California Suite (1978).
Matthau starred in three crime dramas in the mid-1970s, as a detective investigating a mass murder on a bus in The Laughing Policeman (1973), as a bank robber on the run from the Mafia and the law in Charley Varrick (also 1973) and as a New York transit cop in the
Walter Matthau