The crowns, along with a rosary, were taken from a church sanctuary in San Nicolas, some 245 kilometers (150 miles) northeast of the Argentine capital.
The theft was discovered by the church sexton, Carlos Perez, who told local media he found the glass display case broken and the objects missing early Thursday morning.
Both crowns were made of silver with gold inlays, forged from donated medals, rings, and other jewelry, and blessed by the pope, the Catholic News Agency of Argentina reported.
Some 600,000 Argentines, including President Cristina Kirchner, as well as the pope, took turns with metal hammers to help shape the crowns, the agency added.
Pallarols, 70, is a renowned artist who has made ceremonial staffs for several Argentine presidents as well as numerous official gifts.