The crystal structure of B-type Er2O[SiO4] has been determined by single crystal X-ray diffraction. It crystallizes with the (Mn,Fe)2[PO4]F type structure in the monoclinic space group C2/c (a = 14.366(2), b = 6.6976(6), c = 10.3633(16) Å, ß = 122.219(10)°, Z = 8) and shows anionic tetrahedral [SiO4]4– units and non-silicon-bonded O2– anions in distorted [OEr4]10+ tetrahedra. The [(Er1)O6+1] and [(Er2)O6] polyhedra form infinite chains which are connected by common edges.