At the height of his fame, he was one of the most popular actors in German-speaking cinema, and received Bambi Award and Bravo Otto nominations for the honor.

He attended Princeton University, but dropped out to join a theatrical stock company, much to his family's chagrin.

[6] Barker made it to Broadway once, in a small role in a short run of Shakespeare's The Merry Wives of Windsor in 1938.

[7] He also had a small role in Orson Welles's disastrous Five Kings, which met with so many problems in Boston and Philadelphia that it never made it into New York City.

[8] In February 1941, 10 months before the attack on Pearl Harbor, Barker left his fledgling acting career and enlisted in the U.S. Army.

Back at RKO he was in Dick Tracy Meets Gruesome (1947), Berlin Express (1948), Mr. Blandings Builds His Dream House (1948), The Velvet Touch (1948), and Return of the Bad Men (1948), playing Emmett Dalton.

His blond, handsome, and intelligent appearance, as well as his athletic 6'4" frame, helped make him popular in the role Johnny Weissmuller had made his own for 16 years.

[11] Barker had a rare non-Western role in The Price of Fear (1956), a film noir with Merle Oberon.

[22] Barker had a short but compelling role as Anita Ekberg's fiancé in Federico Fellini's La Dolce Vita (1960).

Barker then played Old Shatterhand in an adaptation of the novel by popular German author Karl May (1842–1912), Treasure of the Silver Lake (1962).

His go-to dubber was Gert Günther Hoffmann, whose distinctive voice contributed to Barker's success.

[18] He returned to the United States occasionally and made a handful of guest appearances on American television episodes, but Europe, and especially West Germany, was his professional home for the remainder of his life.