Pate was born Edward John Pate in Drummoyne, New South Wales and attended Fort Street High School. Initially interested in becoming a medical missionary, but unable to afford the university fees due to the Depression, he worked in Sydney before 1938, when he became a Writer and broadcaster for the Australian Broadcasting Commission, collaborating with George Ivan Smith on Youth Speaks. For the remainder of the 1930s, he worked primarily in radio drama. He also published theatrical and literary criticism and enjoyed brief success as an author of short stories, publishing works in both Australia and the United States.

After the war, Pate returned to radio, appearing in many plays and serials. Between 1946 and 1950 he began working in films. In 1949 he appeared in his first leading role in Sons of Matthew. In 1950, he appeared in Bitter Springs with Tommy Trinder and Chips Rafferty. That same year Pate also adapted, produced, and directed two plays: Dark of the Moon and Bonaventure.

In 1951, Pate married Felippa Rock, daughter of American film Producer Joe Rock. The couple had a son, Christopher, also an actor, along with a number of grandchildren and great-grandchildren.

During his time in the United States, Pate became an acting instructor and lecturer, and wrote many screenplays and plays for American films and television series, including Rawhide ("Incident of the Power and the Plow" with Dick Van Patten) and Most Dangerous Man Alive ("The Steel Monster"). In 1959, he returned briefly to Australia, where he starred in a television presentation of Tragedy in a Temporary Town, shown as part of the Shell Presents anthology drama series. After that project he returned to the United States for another eight years, during which time he enjoyed a successful career as a television character actor, appearing repeatedly on programs such as Gunsmoke, Sugarfoot, The Texan, The Rifleman, Branded ("Call to Glory"), Daniel Boone, The Virginian, Perry Mason ("The Case of the Skeleton's Closet" and "The Case of the Wednesday Woman"), Batman (episodes 45 "The Clock King's Crazy Crimes" and 46 "The Clock King Gets Crowned"), Mission: Impossible ("Trek"), The Man from U.N.C.L.E. ("The Foreign Legion Affair"), Get Smart, Rawhide ("Incident of the Power and the Plow", "Incident at Superstition Prairie", "Incident of the Boomerang", and others), Voyage to the Bottom of the Sea, and Wagon Train. In the 1963 movie PT 109, he played the part of Arthur Reginald Evans, the Australian coast watcher who helped rescue John F. Kennedy and his crew. That role was of the few occasions when Pate played an Australian while working in the United States.

In 1966, Pate played Frenchy Godey, a scout for Kit Carson and the John C. Fremont (Dick Simmons) expedition in the episode "Samaritans, Mountain Style" of the syndicated series Death Valley Days. In the storyline of that episode, Carson (Phillip Pine) and Gody stop to help a settler in dire straits. In an earlier Death Valley Days episode, "The Measure of a Man" (1963), Pate was cast as the notorious bandit Augustine Chacon. In that episode, Arizona Ranger Burt Mossman (Rory Calhoun) captures Chacon with the reluctant aid of another outlaw, Burt Alvord (Bing Russell), who has been promised a lenient sentence if he will surrender. Mossman handcuffs Chacon and orders Alvord to throw the key into the bushes. Soon Alvord is returned for the hanging he had avoided some four years earlier. In another 1963 Death Valley Days episode titled "The Peacemaker", Pate portrayed Navajo Chief Hastele. In that episode's plot Mormon pioneer Jacob Hamblin (David Brian) strives desperately to maintain a peace treaty with the Navajo after a white man kills some Indians who had come onto his property.

In 1968, Pate returned to Australia and became a television Producer, winning two Logie Awards while working at the Seven Network. In 1970, he published a textbook on acting, The Film Actor. From 1971 to 1975 he starred as Detective Senior Sergeant Vic Maddern in Matlock Police. After leaving Matlock Police, Pate began working more behind the camera, continuing to work too in theatre in both Sydney and Melbourne. In 1977 he wrote and produced The Mango Tree, starring his son Christopher Pate. In 1979 he adapted the screenplay for Tim from the novel by Colleen McCullough, as well as producing and directing the film, which starred Piper Laurie and Mel Gibson. Pate won the Best Screenplay Award from the Australian Writers Guild for his adaptation.

His film appearances in the 1970s and 1980s included Mad Dog Morgan (1976), introduction in the biopic The Battle of Broken Hill (1981), Duet for Four (1982), The Wild Duck (1984), Death of a Soldier (1986), and Howling III (1987). Pate also appeared as the President of the United States in The Return of Captain Invincible (1982), in which he sings "What the World Needs", a song calling for the return of Captain Invincible to save the world. During the early 1980s Pate also collaborated with his son Christopher in a successful stage production of Mass Appeal at the Sydney Opera House.

Although Michael Pate retired from acting in 2001, he remained busy with voiceover work; and he was writing a screenplay at the time of his death. He died at the age of 88 at Gosford Hospital in New South Wales, Australia, on 1 September 2008.