The crystal structure of the new mineral urusovite Cu[AlAsO₅] has been determined (monoclinic system, sp. gr. P2₁/c, a = 7.335(1) Å, b = 10.255(1) Å, c = 5.599(1) Å, β = 99.79(1)°, V = 415.0(1) ų, Z= 4). The structure is solved by direct methods and refined to R = 0.048 (wR = 0.103). The structure is built by open-branched {uB, ²_∞} [AlAsO₅]^2- layers parallel to the (100) plane. The layers consist of two-link chains of ¹_∞[Al₂O₆] tetrahedra, which are parallel to the z-axis and are connected through the [AsO₄]-groups. The sharing-edges [CuO₅] tetragonal pyramids link the aluminoarsenate layers to form a three-dimensional framework. The established layer is the second example of an tetrahedral aluminoarsenate polyanion.