After transitioning to theater and television in the late 1950s, she starred in productions such as The King and I and appeared on shows like The Twilight Zone and Murder, She Wrote.

After the New York run, the play went on tour, and while performing at the Biltmore Theatre Los Angeles, Blyth was offered a contract with Universal Studios.

After Mildred Pierce, Blyth sustained a broken back while tobogganning in Snow Valley in the Southern California mountains[8] and was not able to fully capitalize on the film's success.

She recovered and made two films for Mark Hellinger's unit at Universal: Swell Guy (1946), with Sonny Tufts, and Jules Dassin's Brute Force (1947) with Burt Lancaster.

[9] Universal lent her to MGM to play the female lead in Killer McCoy (1947), a boxing film with Mickey Rooney that was a box-office hit.

[10] Back at Universal, Blyth did a film noir with Charles Boyer and Jessica Tandy, A Woman's Vengeance (1948), affecting a British accent.

Universal lent Blyth to Paramount Pictures to play the female lead in Top o' the Morning (1949), as Barry Fitzgerald's daughter, who is romanced by Bing Crosby.

In April 1949, Universal suspended her for refusing a lead role in the baby adoption ring crime noir Abandoned; Gale Storm played it.

Back at Universal she made Thunder on the Hill (1951) with Claudette Colbert and had the female lead in The Golden Horde (1951) with David Farrar.

She was top-billed in the comedy Sally and Saint Anne (1952) and was borrowed by RKO for One Minute to Zero (1952), a Korean War drama with Robert Mitchum, wherein she replaced Claudette Colbert, who came down with pneumonia.

[15] On television, Blyth appeared in The Lux Video Theatre version of A Place in the Sun with John Derek and Marilyn Erskine.

Back at MGM, Blyth had the lead in the remake of Rose Marie (1954) with Howard Keel, which earned over $5 million, but lost money due to high costs.

Blyth was meant to be reteamed with Lanza in The Student Prince (1954), but he was fired from the studio and replaced in the picture by Edmund Purdom;[17] the film did well at the box office.

[25] Blyth performed live in concert tours for many years with Harper MacKay serving as her accompanist and music director.

[26][27][28] In the December 1952 edition of Motion Picture and Television Magazine, Blyth stated in an interview that she was a Republican who had endorsed Dwight D. Eisenhower for president, the month before during the 1952 presidential election.

[33] In 1973, she and McNulty, both Roman Catholics were accorded the honorific rank of Lady and Knight of the Holy Sepulchre in a ceremony presided over by Cardinal Cooke.