The crystal structure of filatovite, K[(Al,Zn)₂(As,Si ₂O₈] (monoclinic, I2/c, a = 8.772(1), b = 13.370(2, c = 14.690(2) Å, β = 115.944(6)°, V = 1549.1(4) ų) has been solved by direct methods and refined to R₁ = 0.033 on the basis of 1959 unique observed reflections with |F_o| ≥ 4σF. It is isotypic with the structures of celsian, Ba[Al₂Si₂O₈], and its synthetic analogues. The structure contains four symmetry independent tetrahedral sites. The T(1) and T(4) sites have the same refined occupancy of As_0.55Si_0.45 and are characterized by average <T-O> bond lengths of 1.634 Å. The occupancies of the T(2) and T(3) sites are Al_0.94Zn_0.06 and Al_0.96Zn_0.04, respectively, with average <T(2 -O> and <T(3)-O> bond lengths of 1.753 and 1.754 Å, respectively. Consistent with Al-Si ordering in celsian, (As,Si O₄ tetrahedra are surrounded by (Al,Zn)O₄ tetrahedra and vice versa. One symmetry independent K⁺ cation resides in framework cavities and is coordinated by nine O atoms with the average <K-O> bond length of 3.02 Å. Incorporation of pentavalent T⁵⁺ cations into the feldspar-like tetrahedral framework is possible if it is accompanied by incorporation of T²⁺ and T³⁺ cations into adjacent tetrahedral sites.