The couple tied the knot in front of family and friends at the Kennedy family compound at Hyannis Port on Cape Cod, Massachusetts, saying their vows in a marquee at the home formerly owned by President Kennedy and his wife Jackie.
Cheryl, who has previously received two Emmy nominations for her role as Larry David's wife in Curb Your Enthusiasm, wore an elegant strapless white dress and silver strappy heels.
Robert F Kennedy Jr and Cheryl Hines have been together since 2011
The 48-year-old bride, who became engaged to 60-year-old Robert in May, wore her blonde locks in a chic up-do.
Cheryl and Robert, an environmental lawyer and activist, live together in New York.
Speaking shortly after becoming engaged to Robert, who has been married twice before, Cheryl told People she was "surprised" and "thrilled".
The couple married in a marquee at the home formerly owned by President Kennedy
"It's fun that the two families are coming together," she said. "It's very sweet that way. I come from a big family and the Kennedys are a big family. It feels natural. It feels fun.
Ten facts about iconic US President John F Kennedy and First Lady Jackie
"It feels great because you know you're going to be with the person you really like to be with for a very long time," she added. "And that's a great feeling."
Cheryl has a daughter called Catherine Rose Young from her marriage to producer Paul Young, while Robert is father to six children, Bobby Kennedy III, Kyra LeMoyne Kennedy, Conor Richardson Kennedy, William Finbar Kennedy, Aiden Caohman Vieques Kennedy, Kathleen Alexandra Kennedy.