No information has been released about the identity of the expectant mother. She is believed to be seven months pregnant after a brief relationship which took place over the festive season last year while Jude was filming Sherlock Holmes in New York.
Thirty-six-year-old Jude - who is currently single - said he would play a "fully supportive" role in the child's life, despite no longer being involved with the mother-to-be.
His representative said: "Jude Law has been advised by the birth mother that he is to be the father of a child due in the autumn of this year.
"This is an entirely private matter and no further statements will be made."
Jude already has three children – Rafferty, 12, Iris, eight, and son Rudy, six – from his seven-year marriage to Sadie Frost. They divorced in 2003.