Marlowe debuted on televsion in 1951 on Pulitzer Prize Playhouse (1950–52) in the episode “Hostage” (June 8, 1951) His first feature film role was in the 1954 production of Attila. Two years later, he starred as John Goodwin in an episode “In Summer Promise” on General Electric Theater. He appeared as Jimmy Budd, along with Reagan and his wife Nancy Davis, in the episode “The Long Shadow” in Dick Powell’s Zane Grey Theater directed by Budd Boetticher, which aired on January 19, 1961. Marlowe often took film roles of dysfunctional juveniles in a series of films made during the 1950s and 1960s, including The Scarlet Hour (1956), The Restless Breed (1957), Riot in Juvenile Prison (1959), The Subterraneans (1960), and A Cold Wind in August (1961). In 1956, Marlowe appeared as Knox Cutler in the western film The Young Guns. In 1958, he began appearing in a number of television westerns, with his guest role of Jess “Little Elk” Carswell on NBC’s Wagon Train with Ward Bond. In 1959, he portrayed the outlaw John Wesley Hardin, who reportedly killed forty-four men in the Old West, in the episode “The Turning Point” of ABC’s Bronco. In 1960, he appeared as “The Kid from Nowhere” in CBS’s one-season Hotel de Paree starring Earl Holliman and Jeanette Nolan. That same year, he starred as Mickey Free in the episode “Apache Blood” of Clint Walker’s ABC series, Cheyenne. He starred in 1960 as Clancy Jones in the episode “The Show-Off” in NBC’s Law of the Plainsman starring Michael Ansara. He appeared on CBS’s Dick Powell’s Zane Grey Theater Marlowe guest starred three times in significant segments of Have Gun – Will Travel. Marlowe appeared four times between 1963 and 1966 on James Arness’s CBS western Gunsmoke. In 1964, Marlowe appeared as Lee Hewitt in the episode “The Roper” on NBC’s most successful western, Bonanza. In 1970, he guest starred as Billy Kells in the episode “The Experiment” on CBS’s Lancer series starring Andrew Duggan, James Stacy, and Wayne Maunder.

In the 1960s, Marlowe continued to appear in drama and adventure series, often as a young man in trouble with the law or unwilling to adjust to societal mores. He appeared twice in 1961 on ABC’s Target: The Corruptors! crime drama in episodes “A Man’s Castle” (as Tito) and “Mr. Meglomania” (as Phil Manzak). In 1961, he starred as Armand Fontaine a serial killer on the episode “Effigy in Snow” of CBS’s Route 66. He guest starred as Eliot Gray in the 1961 episode “The Throwback” of CBS’s Alfred Hitchcock Presents. He appeared on Thriller, Dr. Kildare, and The Detectives. In 1962, he appeared on Checkmate, with Anthony George, Doug McClure, and Sebastian Cabot. Other appearances in 1962 were on NBC’s newspaper drama Saints and Sinners with Nick Adams and on ABC’s Stoney Burke, a drama about a rodeo performer, in which Marlowe played the character Soames Hewitt in the episode “Point of Honor”. In 1962, Marlowe appeared in NBC’s psychiatric drama, The Eleventh Hour, with Wendell Corey and Jack Ging, in the role of Stanley Filmore in the episode “Where Have You Been, Lord Randall, My Son?” His 1963 appearances were also on three ABC medical series: The Nurses, Ben Casey, and Breaking Point, the latter a psychiatric drama starring Paul Richards, in which Marlowe appeared as Jason Landros in the episode “Solo for B-Flat Clarinet”. He appeared twice on ABC’s science fiction series The Outer Limits in the 1963-1964 season. Between 1966 and 1973, Marlowe appeared ten times on ABC’s crime drama The F.B.I. starring Efrem Zimbalist, Jr. During this time, he appeared on Owen Marshall: Counselor at Law, Ironside, Cannon, Mannix, and Hawaii Five-O. He appeared six times as Nick Koslo on the 1976-77 series Executive Suite, twice on CBS’s Barnaby Jones with Buddy Ebsen, and also appeared in the 1975 film Journey into Fear. His television work continued into the 1980s on ABC’s Matt Houston, T. J. Hooker and Days of Our Lives. He portrayed Keeve Falor in the fifth season episode “Ensign Ro” on Star Trek: The Next Generation.

During the 1990s, Marlowe appeared as Al Brackman twice on Matlock, on Father Dowling Mysteries and on Jake and the Fatman. His most enduring work in the decade was in 1994 with 65 appearances as Michael Burke on the night-time soap opera Valley of the Dolls. In 1995, he appeared as Avery Nugent in the episode “School for Murder” on Murder She Wrote. Marlowe also appeared on stage. His most highly acclaimed such performance was at the Chicago Civic Theatre in a production of Arthur Miller’s Death of a Salesman. He was a founding member of Theatre West in Los Angeles. Marlowe died of a heart attack at age 68 in Los Angeles, California. He never married.