The 37-year-old actress and her husband, Will Kopelman, welcomed a baby girl named Olive Barrymore Kopelman on Sept. 26.
A statement from Chris Miller at Barrymore's production company, Flower Films, said the baby was born "happy, healthy and welcomed by the whole family." The statement didn't provide specifics on the birth.
Barrymore wed Kopelman, an art consultant, in June. He's the son of former Chanel CEO Arie Kopelman.
She is the granddaughter of screen legend John Barrymore.