Born in Scotland as Moira Shearer King, Shearer studied at the Sadler's Wells School and joined the company in 1942. She appeared with Margot Fonteyn and Pamela May in Ashton's Symphonic Variations in 1946 and in the lead in the premiere of his Cinderella in 1948.

That year also saw the release of The Red Shoes, directed by Michael Powell and Emeric Pressburger. The film is a portrait of a ballet troupe led by a tyrannical impresario (based in part on Serge Diaghilev); Shearer's Victoria Page is a dancer torn between her passion for the company and a love affair. Eventually she commits suicide.

When Sadler's Wells Ballet made its successful American debut at the Metropolitan Opera the following year, according to the Times, fans of the film were surprised to discover that Shearer was not cast in the lead role of Sleeping Beauty on opening night.

Shearer later appeared in several other films, including Powell's seminal thriller Peeping Tom in 1960. But Ludovic Kennedy, whom she married in 1950, told the London Independent that "the ballet was the thing to which she was really committed—the film industry was a bit of distraction."