The Grey's Anatomy actress gave birth to son Micah Emmanuel Lanfer on Wednesday evening, reports People.
"She and her husband, Peter Lanfer, are in love with him," her rep told the publication in a statement.
The baby was said to weigh 7lbs, 4oz and was 19 inches long at the time of birth.
Drew initially announced her pregnancy in July 2011. It was not written into her Grey's Anatomy storyline.
Earlier this month, Grey's Anatomy co-star Jessica Capshaw revealed that she and husband Christopher Gavigan are expecting their third child.