The hybrid organic-inorganic uranyl selenate, [K@(C10H20O5)][(UO2)(SeO4)(HSeO4)(H2O)] (I), was prepared by isothermal evaporation from aqueous solutions. The crystal structure of I [orthorhombic, Pnma, a = 15.386(3), b = 10.771(2), c = 13.239(3) Å, V = 2194.0(7) Å3, Z = 4, R1 = 0.042] is based upon complex 15-crown-5-ether-uranyl-selenate polymeric units consisting of uranyl selenate chains decorated by [K@(15-crown-5)]+ complexes via strong ionic K+–O bonds. The 1D hybrid units are packed in a parquetted-like fashion and connected to each other by hydrogen bonds and residual van der Waals interactions.This work was supported by St. Petersburg State University (grant 3.38.136.2014) and President of Russian Federation grant for young scientists (no. MK-1737.2014.5 to V. V. G.). The XRD studies have been performed at the X-ray Diffraction Centre of St. Petersburg State University.