Thorne-Smith delivered the baby - her first - at Cedars-Sinai Medical Center on Friday, Samfilippo said.
The father is Thorne-Smith's husband Roger Fishman, a media consultant. The couple named the boy Jacob Emerson Fishman.
Thorne-Smith, 40, is known for roles in several TV shows including "Melrose Place," "Ally McBeal" and "According to Jim."