Acting career
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. Merrill made her debut on the stage in the play The Mermaids Singing in 1945.
During the late 1950s and 1960s, Merrill was believed to have been marketed as a replacement for Grace Kelly, and in 1959, she was proclaimed "Hollywood's new Grace Kelly".
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).
Merrill appeared in numerous television series in the 1960s, such as playing the villain Calamity Jan in two 1968 episodes of Batman with then-husband Cliff Robertson. She also made guest appearances on two Bonanza episodes as Susannah Clauson, The Alfred Hitchcock Hour episode "Bonfire" (1962), The Investigators, The Bold Ones, Wagon Train (1964), Mission: Impossible, The Love Boat; Quincy, M.E.; Murder, She Wrote; Roseanne, and The Nanny, as Maxwell Sheffield's disapproving and distant British mother. In 1971, Merrill appeared as Laura Duff in The Men from Shiloh (rebranded name for the TV Western The Virginian) in the episode titled "The Angus Killer".
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.
In the 1960s and 1970s, Merrill was a recurring guest on several network television game and panel shows, including Match Game, To Tell the Truth, What's My Line, and Hollywood Squares.