"I'm so excited that (our daughter) Mattea is going to have a sibling. We're going to be a family of four," Sorvino, who is due this summer, tells PEOPLE.
The couple's first child, Mattea Angel, was born in November of 2004. Shortly after the birth, Backus told PEOPLE: "(Mattea) is the cutest little baby in the whole wide world."
Sorvino, 38, and Backus, 24, married in June of 2004. They met at a friend's charades party the previous August. "He walked into the kitchen looking for silverware. We saw each other and something made us want to talk to each other more," Sorvino told PEOPLE of the couple's first encounter.
"Mira looked like a young girl in seventh heaven," one witness told PEOPLE of the Italian ceremony.
Sorvino, who is the daughter of actor Paul Sorvino, won an Academy Award for Best Supporting Actress for her role in Woody Allen's 1995 film Mighty Aphrodite.
She is nominated for a Golden Globe this year for her role in the Lifetime miniseries Human Trafficking.
Up next is a role in the CBS miniseries The Hades Factor. Backus, also an actor, recently wrapped the upcoming film All In, about the World Series of Poker.
To read more about Mira Sorvino, pick up the new issue of PEOPLE on newsstands Friday.