Sorvino gave birth to the couple's second child, Johnny, on Monday at Cedars-Sinai Hospital in Beverly Hills, Calif. The infant weighed 7 pounds, 14 ounces.
"The baby is healthy and happy, and mother and the rest of the family are very, very excited," Sorvino's representative, Ed Choi, told The Associated Press on Tuesday.
Sorvino, 38, and Backus, 24, have an 18-month-old daughter, Mattea Angel. The couple were married in 2004.
Sorvino, the daughter of actor Paul Sorvino, won an Oscar for her role in Woody Allen's 1995 comedy, "Mighty Aphrodite."
Backus has appeared on the Fox drama "The O.C." and the NBC sitcom "Will & Grace."