Memorable films and TV programs that Sullivan appeared in include The Great Gatsby, The Bad and the Beautiful, Forty Guns, The Price, and Pat Garrett and Billy the Kid.

You're Out (1936), Broker's Follies (1937), Dime a Dance (1937) (alongside Imogene Coca, June Allyson and Danny Kaye), Dates and Nuts (1937), and Hi-Ho Hollywood (1937).

In 1950, Sullivan replaced Vincent Price in the role of Leslie Charteris' Simon Templar on the NBC Radio show The Saint.

He had a supporting part in High Explosive (1943) for Pine-Thomas Productions, who released through Paramount, and he was the second male lead in The Woman of the Town (1943) with Claire Trevor.

[8] He was signed to a long term contract by Paramount, who gave him a good support role in an "A" film, the musical Lady in the Dark (1944) with Ginger Rogers.

He supported Dorothy Lamour in Rainbow Island (1944) and Alan Ladd and Loretta Young in And Now Tomorrow (1944), and was one of many Paramount names in Duffy's Tavern (1945).

[10] Then he went to Monogram Pictures for Suspense (1946), the most expensive film that studio had made to date, produced by the King Brothers; Sullivan was second billed to Belita.

MGM signed Sullivan to a contract, and he played supporting roles in Tension (1950), The Outriders (1950), Nancy Goes to Rio (1950), A Life of Her Own (1950), and Grounds for Marriage (1951).

(1951) with Young and Payment on Demand (1951) with Bette Davis at RKO but was back down the cast list for Three Guys Named Mike (1951), Mr. Imperium (1951), and Inside Straight (1951).

[12] Sullivan played the lead in a series of lower budgeted films noir: Loophole (1954) for Allied Artists, Playgirl (1954) at Universal, and The Miami Story (1954) for Sam Katzman.

[13] He went to Paramount to support James Stewart in Strategic Air Command (1955) and guested on shows like General Electric Theater, Studio One in Hollywood, Climax!

He guest starred on Perry Mason, Mission: Impossible, Bonanza, Garrison's Gorillas, Mannix, The Man from U.N.C.L.E., That Girl, and It Takes a Thief.