Single crystals of Cs₂(UO₂)(NO₃)Cl ₃ were prepared by a hydrothermal method at 205 °C. The crystal structure has been solved by Direct Methods: monoclinic, P21/n, a = 10.3748(13), b = 9.4683(13), c = 12.5535(16) Å β = 110.280(2)°, V = 1156.7(3) ų, R1 = 0.029. In the structure, strongly bonded linear uranyl cations UO2 2+ are equatorially coordinated by two O and three Cl atoms to form (UO₂)Cl₃O₂ pentagonal bipyramids. Each bipyramid shares its O-O edge with an adjacent (NO3)? anion to form finite clusters with the chemical composition [(UO₂)(NO₃)Cl ₃]^2?. The Cs⁺ cations provide three-dimensional connectivity of the structure by forming Cs-O and Cs-Cl contacts to the uranyl nitrate chloride complexes. Related structures of mixed-ligand uranyl halides are compared.