The 36-year-old actress is set to take on a role opposite 'Friday Night Lights' actor Kyle Chandler in the TV show, reported Daily Star.
The show is a thriller about spirituality, power and politics set against the modern-day political machinations within the Catholic church.
Friel will play Kayla Duffy, the younger sister of Chandler's character Cardinal Thomas Duffy.
Matthew Goode will play Papal Secretary Bernd Koch while Sebastian Koch is set to star as Cardinal Marco Malerba.
Production is set to begin in Rome next month.