A spokesman said Thursday that negotiations are still taking place, but Boyle is expected to sing at an open-air papal Mass in Glasgow's Bellahouston Park on Sept. 16.
Benedict's four-day trip will be the first papal visit to Britain since Pope John Paul II in 1982.
His itinerary also includes an address in Parliament and the beatification of 19th-century Catholic convert Cardinal John Henry Newman.
Forty nine-year-old Boyle became an overnight sensation after her appearance last year on a TV talent show was viewed millions of times on the Internet. Her debut album became a global best-seller.