On advice from her half-sister’s (then) husband, she adopted the stage name Dina Merrill, borrowing from Charles E. Merrill, a famous stockbroker like her father. Dina Merrill made her debut on the stage in the play The Mermaid Singing in 1945. During the late 1950s and 1960s, Merrill was believed to have intentionally been marketed as a replacement to Grace Kelly, and in 1959 she was proclaimed “Hollywood’s new Grace Kelly”. Dina Merrill’s film credits included Desk Set (1957), A Nice Little Bank That Should Be Robbed (1958), Don’t Give Up the Ship (1959), Operation Petticoat (1959, with Cary Grant, who had been married to her cousin, Woolworth heiress Barbara Hutton), The Sundowners (1960), BUtterfield 8 (1960), The Young Savages (1961), The Courtship of Eddie’s Father (1963), I’ll Take Sweden (1965), The Greatest (1977), A Wedding (1978), Just Tell Me What You Want (1980), Anna to the Infinite Power (1983), Twisted (1986), Caddyshack II (1988), Fear (1990), True Colors (1991), The Player (1992), Suture (1993) and Shade (2003). She also appeared in made-for-TV movies, such as Seven in Darkness (1969), The Lonely Profession (1969), Family Flight (1972) and The Tenth Month (1979).

Dina Merrill appeared in numerous television series in the 1960s, such as playing the villain, “Calamity Jan,” in two 1968 episodes of Batman alongside then-husband Cliff Robertson. She also made guest appearances on Bonanza, The Bold Ones,The Love Boat, Murder She Wrote and The Nanny, as Maxwell Sheffield’s disapproving and distant British mother. Her stage credits include the 1983 Broadway revival of the Rodgers and Hart musical On Your Toes, starring Russian prima ballerina Natalia Makarova. In 1991, she appeared in the rotating cast of the off-Broadway staged reading of Wit & Wisdom. In 1991, Merrill and her third husband, Ted Hartley, merged their company, Pavilion Communications, with RKO to form RKO Pictures, which owns the intellectual property of the RKO Radio Pictures movie studio. On May 22, 2017, Dina Merrill died at her home in East Hampton, New York. She had been suffering from dementia with Lewy bodies.