In the course of our ongoing study of thorium tantalates, crystals of an unusual thorium borate phosphate, Th2[BO4][PO4], were formed by the reaction of thorium(IV) nitrate, phosphorus pentoxide (molar ratio 2:1) and the fluxing agent boron oxide at 1200°C. The colorless and platy crystals of Th2[BO4][PO4] are monoclinic, space group P21/c (no. 14), a 8.4665(2), b 7.9552(2), c 8.2297(1) Å, β 103.746(1)° and Z = 4. Face-sharing [ThO9]14− and [ThO10]16− polyhedra form a double layer that is parallel to (100). The [BO4]5− tetrahedra are located between the layers of Th polyhedra within the double layer. These double layers are connected through [PO4]3− tetrahedra.