Crystals of UO{sub 2}CrO{sub 4}(C{sub 5}NH{sub 5}COO){sub 2}(H{sub 2}O)] {center_dot} 2H{sub 2}O are synthesized and their structure is studied by X-ray diffraction. The compound crystallizes in the triclinic crystal system. The unit cell parameters are as follows: a = 7.0834(10) Angstrom-Sign , b = 10.6358(14) Angstrom-Sign , c = 12.9539(17) Angstrom-Sign , {alpha} = 75.096(2) Degree-Sign , {beta} = 74.490(2) Degree-Sign , and {gamma} = 80.657(2) Degree-Sign ; V = 904.1(2) Angstrom-Sign {sup 3}, space group P1-bar, Z = 2, and R = 0.026. The structure is built of [UO{sub 2}CrO{sub 4}(C{sub 5}NH{sub 5}COO){sub 2}(H{sub 2}O)]{sub 2} centrosymmetric dimers, which are linked into a framework by a system of hydrogen bonds involving inner-sphere and outer-sphere water molecules. The coordination number of the U(VI) atom is seven, and the coordination polyhedron is a pentagonal bipyramid with the oxygen atoms of the uranyl group, two chromate groups, two molecules of isonicotinic acid, and a water molecule at the vertices. The crystal chemical formula of the [UO{sub 2}CrO{sub 4}(C{sub 5}NH{sub 5}COO){sub 2}(H{sub 2}O)]{sub 2} dimer is represented as AB{sup 2}M{sub 3}{sup 1}, where AB{sup 2}M{sub 3}{sup 1}, where A = UO{sub 2}{sup 2+}, B{sup 2} = CrO{sub 4}{sup 2-}, and M{sup 1} =more » = C{sub 5}NH{sub 4}COOH and H{sub 2}O.« less