Born in New York City, she is the daughter of Wall Street wizard Edward Francis Hutton and Post Cereals heiress Marjorie Merriweather Post.

Using the stage name Dina Merrill her first film was Desk Set (1957), in which she played Sylvia Blair, one of the researchers whose supervisor was Bunny Watson (Katharine Hepburn).

Dina Merrill has been married three times. Her first husband was Stanley Rumbough, Jr., an heir to the Colgate toothpaste fortune. Married in 1946, they divorced in 1966. They had three children. Her second husband was the American actor Cliff Robertson (married 1966, divorced 1986). They had one daughter, Heather Robertson.

Her current husband is former actor Ted Hartley; they have been married since 1989.

A corporate remnant named RKO Pictures was purchased by Merrill and Hartley in 1989 with a plan to resurrect it as a motion picture production company.

On April 6, 2005, in New York City, at the Museum of Television and Radio, of which she is a member of the Board of Directors, Ms. Merrill introduced a screening of Budd Schulberg's 1959 TV production What Makes Sammy Run?. She was in this production. Mr. Schulberg was also at the screening.

Dina Merrill is a significant shareholder and director of Lehman Brothers and serves as the chairman of the Nominating and Corporate Governance Committee and is a member of the Bank's Compensation and Benefits Committee. Ms. Merrill is a presidential appointee to the Board of Trustees of the John F. Kennedy Center for the Performing Arts, a trustee of the Eugene O'Neill Theater Foundation, a vice president of the New York City Mission Society, and serves on the Board of the Juvenile Diabetes Foundation. She is also a member of the Board of ORBIS International, a global, nonprofit organization dedicated to preventing blindness through education and transferring the medical skills to treat and prevent blindness in developing countries.

She is a pro-choice Republican.