Single crystals of γ‐K(UO2)(NO3)3 were prepared from aqueous solutions by evaporation. The crystal structure orthorhombic, Pbca (61), a = 9.2559(3) Å, b = 12.1753(3) Å, c = 15.8076(5) Å, V = 1781.41(9) Å3, Z = 8 was determined by direct methods and refined to R1 = 0.0267 on the basis of 3657 unique observed reflections. The structure is composed of isolated anionic uranyl trinitrate units, (UO2)(NO3)3–, that are linked through eleven‐coordinated K+ cations. Both known polymorphs of K(UO2)(NO3)3 (α‐ and γ‐phases) can be considered as based upon sheets of isolated complex (UO2)(NO3)3– ions separated by K+ cations. The existence of polymorphism in the two KUO2(NO3)3 polymorphs is due to the different packing modes of uranyl trinitrate clusters that adopt the same two‐dimensional but different three‐dimensional arrangements.