A medical student, he gave up that career for the theatre.
By 1921, was in movies: Not Guilty (21, Sidney Franklin); Poverty of Riches 121, Reginald Barker); The Sin Flood (22, Frank Lloyd); Yellow Men and Gold (22, Inin V. Willat); Fools First (22, Marshall Neilan); and The Bonded Woman (22, Phil Rosen). After going to England to make The Christian (23, Maurice Tourneur), he was put under contract by Paramount as a replacement for Wallace Reid.
He stayed with that studio until 1929, very successful il seldom in their most notable films: Racing Hearts (23, Paul Powell); The Woman with Four Faces (23, Herbert Brenon); To the Last Man (23, Victor Fleming); The Call of the Canyon (23, Fleming); in the modern section of The Ten Commandments (23, Cecil B. De Mille); The Stranger (24, Joseph Henabery); Sinners in Heaven (24, Alan Crosland); Unguarded Women (24, Crosland); Too Many Kisses (25, Paul Sloane); Men and Women (25, William De Mille); Lucky Devil (25, Frank Tuttle); and The Vanishing American (25, George B. Seitz). He was in a handful of Gregory La Cavas films: Womanhandled (25); Let’s Get Married (26); Say It Again (26); Paradise for Two (27); and The Gay Defender (27).
But by the late 1920s, Dix and Paramount were already on bad terms, partly because he preferred to work in New York: Knockout Reilly (27, Malcolm St. Clair); Man Power (27, Clarence Badger); Sporting Goods (28, St. Clair); Easy Come, Easy Go (28, Tuttle); Redskin (29, Victor Schertzinger); and Nothing But the Truth (29, Schertzinger). He moved on to RKO and thrived briefly: Seven Keys to Baldpate (29, Barker); Lovin' the Ladies (30, Melville Brown); Shooting Straight (30, George Archainbaud); Edna Ferbers adventurer in Cimarron, Young Donovans Kid (31. Fred Niblo); The Lost Squadron (32, Archainbaud); The Roar of the Dragon (32, Ruggles); Hell's Highway (32, Rowland Brown); and The Conquerors (32, William Wellman). Only rarely thereafter did he have lead parts or big films: The Great Jasper (33, J. Walter Ruben); Stingaree (34, Wellman); The Arizonian (35, Charles Vidor); The Tunnel (35, Maurice Elvey) in Britain; Blind Alley (38, Vidor); Here I Am a Stranger (39, Roy del Ruth); Reno (39, John Farrow); Badlands of Dakota (41, Alfred E. Green); American Empire (42, William McGann); and The Ghost Ship (43, Mark Rohson).
At the end of his career, he played the title role in a series of cheap thrillers, made by William Castle, and based on the radio character: The Whistler (44); The Mark of the Whistler (44); then the Power (45), Voice (45); and Secret of the Whistler (46). His last film was The Thirteenth Hour (47, William Clemens).