"We are overwhelmed with love and joy at the birth of our daughter Clover Clementyne Watson," Wagner and her longtime boyfriend, actor Barry Watson, told People.com in a statement Monday.
The child was born May 30. She weighed 7 pounds, 2 ounces and measured 19 1/2 inches long, the celebrity news Web site said.
Wagner is the daughter of late actress Natalie Wood and film producer Richard Gregson. Her stepfather is actor Robert Wagner.
Watson has two sons from a prior marriage.