A statement issued by the England and Wales Cricket Board (ECB) said: "Holly Flintoff was born at 3.52am (0252GMT) today (Monday) weighing 6lb 2oz. Mother and daughter are both fine."
Flintoff, 26, missed Sunday's defeat against India at Lord's to accompany Rachael to a Cheshire hospital.
He now is expected to meet up with his England teammates later this week ahead of the ICC Champions Trophy.
Hosts England play their first match of the tournament, against Zimbabwe, at Edgbaston on Friday.