The couple's second child was born Monday evening at Cedars-Sinai Hospital. Born a week before Sorvino's due date, the baby boy weighed 7 pounds, 14 ounces and was 21 inches long.
"Both mother and son are doing very well and are both very healthy," publicist Ed Choi told People. "The entire family is thrilled at the addition of a baby brother for their daughter, Mattea."
Sorvino, 38, and Backus, 24, married in June 2004 and Mattea Angel born in November 2004.
Sorvino's father is actor Paul Sorvino. She won her Academy Award for her work in Woody Allen's 1995 "Mighty Aphrodite."