Van Cleef served in the United States Navy during World War II aboard a minesweeper, earning a Bronze Star for his actions.

After acting on stage in regional theatre, he made his film debut in the Oscar-winning Western High Noon (1952) in a non-speaking outlaw cast role.

With distinctive, angular features and a taciturn screen persona, Van Cleef was typecast as minor villain and supporting player in Westerns and crime dramas.

Van Cleef appeared in films such as The Good, the Bad and the Ugly (1966), The Big Gundown (1967), Death Rides a Horse (1967), Day of Anger (1967), Beyond the Law (1968), Commandos (also 1968), Sabata (1969) and its sequel Return of Sabata (1971), Barquero (1970), El Condor (also 1970), Captain Apache (1971),The Magnificent Seven Ride!

[3][4] After completing his military training, Van Cleef was assigned to a submarine chaser and then to a minesweeper called the USS Incredible, on which he worked as a sonarman.

In January 1945, Incredible moved to the Black Sea, and performed sweeping duties out of the Soviet Navy base at Sevastopol, Crimea.

[7] Van Cleef received his first acting role as George in the play Our Town at the Little Theater Group in Clinton, New Jersey.

[9][10] In 1952, he made his television debut when he was cast in the episode "Formula for Fear" of the Western aviation series Sky King.

[13] In 1958, he was cast as Ed Murdock, a rodeo performer trying to reclaim the title in the event at Madison Square Garden in New York City, on Richard Diamond, Private Detective.

In 1958, he was cast as Deputy Sid Carver in the episode "The Great Stagecoach Robbery" of another syndicated Western series, Frontier Doctor, starring Rex Allen.

Van Cleef was cast with Pippa Scott and again with Chuck Connors in the 1960 episode "Trial by Fear" of the CBS anthology series The DuPont Show with June Allyson.

A young Van Cleef also made an appearance on The Andy Griffith Show and as Frank Diamond in The Untouchables, in an episode entitled "The Unhired Assassin".

[17] Leone then chose Van Cleef to appear again with Eastwood, this time as the primary antagonist, Angel Eyes, in the now seminal Western The Good, the Bad and the Ugly (1966).

In two of his final Westerns, he co-starred with Leif Garrett in God's Gun (1976) and Kid Vengeance (1977), both of which were filmed mainly in Israel.

[23] Despite suffering from heart disease from the 1970s and having a pacemaker installed in the 1980s,[24] Van Cleef continued to work in films until his death on December 16, 1989.

[27] He was buried at Forest Lawn Memorial Park Cemetery, Hollywood Hills, California, with an inscription on his grave marker reading "BEST OF THE BAD", referring to his many notable acting performances as a villain.