The Up in the Air star and her husband Renn Hawkey welcomed little Gytta Lubov Hawkey last week (04Nov10).
A spokesperson for Farmiga tells People.com the new addition is "happy and healthy".
Gytta is the couple's second child - they also have a son, Fynn, 22 months.
The Up In The Air star and husband Renn Hawkey are set to welcome their second child next month (Oct10), but rather than take time off, Farmiga carried on with her punishing schedule.
She has been busy directing and starring in Higher Ground, an adaption of born-again Christian Carolyn Briggs' memoir, This Dark World: A Memoir of Salvation Found and Lost - and Farmiga is pleased she carried on with the project.
She says, "I've been working on it for the whole summer in my second trimester of pregnancy which was tough.
"I directed it and starred in it simultaneously. It was a super-low budget film which traces a little girl through childhood, teenage pregnancy and adulthood in search for 'higher ground'. It was wild to be on the other side of the camera!"
The actress, who gave birth to baby Finn just before starting work on Up in the Air in 2009, is due in October (10), according to In Touch magazine.
The baby news has forced Farmiga, who is married to Renn Hawkey, to give up a role as Gerard Butler's wife in upcoming movie Machine Gun Preacher.
An insider tells the publication, "The role would have meant travelling to Africa this summer, but because her baby is due in the fall, she would have been too far along to make the trip."
Farmiga is still planning to continue with plans to make her directorial debut this year (10) by turning born-again Christian Carolyn Briggs' memoir, This Dark World: A Memoir of Salvation Found and Lost, into a movie. The adaptation will be called Higher Ground.