“Sign Her. Jack Warner.”

With that cable from the Warner Bros. movie mogul to his London office, South African-born child actress Sybil Jason launched a career as his studio’s answer to the dominant American moppet of the 1930s, Shirley Temple.

Ms. Jason, who died Aug. 23 at 83, was a button-nosed, bright-eyed scene stealer who developed a following on the British vaudeville circuit with her comic impressions of Greta Garbo and Maurice Chevalier before drawing Warner’s interest in 1935.

At the time, Warner Bros. hoped to tap into the gold mine Temple had created at the competing Twentieth Century Fox studios. Depression-era movie audiences were forking over money to see Temple’s triple-threat of dimpled adorableness: she sang, she danced, and she could break your heart as a plucky orphan.

Ms. Jason became one of the first major child stars at Warner Bros., a studio that had long specialized in gritty gangster dramas and had scant practice developing young actors. The studio cast Ms. Jason in films whose plots bore suspicious resemblance to Temple’s movies.

Ms. Jason crooned with Al Jolson in “The Singing Kid” (1936), summoned a tsunami of tears in “Little Big Shot” (1935) with Robert Armstrong and befriended a spinner of tall tales in “The Captain’s Kid” (1936) with Guy Kibbee. She also rode Seabiscuit in the movie short “A Day at Santa Anita,” set at the racetrack.

Some critics found Ms. Jason a welcome distraction from Temple-mania. “Among child actresses, Sybil Jason is to Shirley Temple as Jean Harlow is to Ann Harding: less wholesome but more refreshing,” Time magazine wrote in 1936.

Ultimately, Ms. Jason could not dent Temple’s popularity. There was speculation that ticket buyers could not penetrate Ms. Jason’s South African accent, but the quality of her film work was undoubtedly a major factor.

When Warner Bros. let her go, Ms. Jason signed with Twentieth Century Fox and supported Temple in two Technicolor productions: Ms. Jason played the cockney scullery maid Becky at a boarding school in the drama “The Little Princess” (1939) and the crippled Angela in the fantasy drama “The Blue Bird” (1940).

In later interviews, Ms. Jason said Temple’s mother demanded that the studio scissor the most dramatic footage of Angela tossing aside her crutches and attempting to walk unsupported. Ms. Jason said Temple’s mother thought parts of the scene would overshadow her daughter’s role.

Sybil Jason said she and Temple remained close over the decades, watching each other’s old movies and dining out. At one Beverly Hills restaurant, Ms. Jason told a British newspaper, a fellow dinner approached them gingerly.

It was Mick Jagger of the Rolling Stones.

“I saw him keep looking over at us,” Ms. Jason said. “Then he crept over, making sure Shirley wasn’t in the middle of her meal. I thought him very un-rock-star-like and an absolute gentleman.”

Sybil Jacobson was born Nov. 23, 1927, in Cape Town, South Africa. She showed early aptitude for singing, dancing and impressions.

An uncle in London, pianist Harry Jacobson, was a musical accompanist to prominent entertainers such as Gracie Fields. He arranged for Sybil to appear at the London Palladium music hall, leading to a walk-on role in the 1935 film “Barnacle Bill.” This led to her work at Warner Bros., where her other films included “The Great O’Malley (1937), with Pat O’Brien and Humphrey Bogart, and “I Found Stella Parish” (1935), with Kay Francis.

Ms. Jason was on a publicity tour in South Africa for Twentieth Century Fox when the United States entered World War II. She remained in her native country for years, hosting a radio program and entertaining Allied troops.

In 1947, she married Anthony Drake, a writer. He died in 2006. Survivors include a daughter, Toni Rossi, and a grandson.

Ms. Jason’s death, in North­ridge, Calif., was confirmed by Gary Heckman, who formerly ran her fan club. He said she had chronic obstructive pulmonary disease.

In contrast with many child actresses, Ms. Jason spoke warmly about her experiences.

“It was like walking into a fairytale book and becoming one of its characters,” she wrote of the Warner Bros lot in her memoir, “My Fifteen Minutes.”