Mohr made more than 500 appearances in radio roles throughout the 1930s, ’40s, and early ’50s. One of his early starring roles on radio was as a replacement for Matt Crowley for a brief interval in Jungle Jim in 1938. He starred as Raymond Chandler’s hardboiled detective, Philip Marlowe, 1948–1951, in 119 half-hour radio plays. He also starred in The Adventures of Bill Lance, and as Michael Lanyard in The Lone Wolf.

Mohr’s son, Anthony Jeffrey Mohr, was born in 1947 and later became a judge in the Los Angeles Superior courts.

In 1954–1955, he starred as Christopher Storm in 41 episodes of the third season of Foreign Intrigue, produced in Stockholm for American distribution. During several episodes of Foreign Intrigue, but most noticeably in “The Confidence Game” and “The Playful Prince”, he can be heard playing on the piano his own musical composition, “The Frontier Theme”, so called because Christopher Storm was the owner of the Hotel Frontier in Vienna. Foreign Intrigue was nominated for an Emmy Award in 1954 under the category “Best Mystery, Action or Adventure Program” and again in 1955 under the category “Best Mystery or Intrigue Series”.

Mohr made four guest appearances on Perry Mason (1961–66). In his first appearance, he played Joe Medici in “The Case of the Unwelcome Bride”. In 1963, he played murder victim Austin Lloyd in “The Case of the Elusive Element”. In 1964, he played the murderer, Alan Durfee, in “The Case of a Place Called Midnight”. In 1966, he played agent Andy Rubin in the series’ final episode, “The Case of the Final Fadeout”.

In 1964 Mohr, together with his second wife Mai, planned the formation of an international film company, headquartered in Stockholm, with Swedish and American writers. The company was to have featured comedy, adventure, crime, and drama shows for worldwide distribution. By then fluent in Swedish, he also planned to star in a film for TV in which his character, a newspaperman, would speak only Swedish. In 1964, he made a comedy Western, filmed in Stockholm and on location in Yugoslavia, called Wild West Story in which, unusually, the good guys spoke Swedish and the bad guys (Mohr, inter alia) spoke in English. He also essayed Captain Vadim, an Iron Curtain submarine commander, in the Voyage to the Bottom of the Sea episode “The Lost Bomb”.

He continued to market his powerful voice, playing Reed Richards (Mister Fantastic) in the Fantastic Four cartoon series during 1967 and Green Lantern in the 1968 animated series Aquaman. In 1968, he appeared in his last film role, as Tom Branca in William Wyler’s Funny Girl, before guest-starring in the TV Western series The Big Valley. He sang in the 1956 Cheyenne episode “Rendezvous at Red Rock”.

Mohr flew to Stockholm in September 1968, to star in the pilot of a proposed television series, Private Entrance, featuring Swedish actress Christina Schollin.