Production on the four-hour miniseries, based on Raymond Khoury's best-selling novel, is to begin in April.
The network said Sorvino will play Tess Chaykin, "a Manhattan archaeologist drawn into a fast-paced, romantic adventure concerning the lost secrets of the medieval Knights Templar."
Garber will play Monsignor De Angelis, a man who "steps in to help with the investigation" to retrieve a lost artifact.
Sorvino won an Oscar for her work in "Mighty Aphrodite." She recently starred in the big-screen drama "Reservation Road."
Best known for his role on TV's "Alias," Garber can now be seen on the series "Eli Stone."
He also has appeared in the films "Sleepless in Seattle," "Legally Blonde" and "Titanic."