6-Aminoquinolinium bis(citrato)borate dihydrate [(6 NH2C9H6NH)(C6H6O7)2B]•2H2O (I) has been synthesized for the first time. The single crystals have been obtained and the full X-ray diffraction analysis of the title compound has been carried out. The structural units of the compound I crystal are large complex bis(citrato)borate anions possessing a spiran structure, 6-aminoquinolinium cations and two molecules of crystallization water. In complex anion two citric acid molecules are bidentately coordinated to the boron atom via the O atoms of central carboxyl and α-hydroxyl groups. The complex anion has pseudosymmetry C2. In 6-aminoquinoline molecule is protonated the nitrogen atom of the heterocyclic ring. The non-hydrogen atoms in 6-aminoquinolinium cation (except the nitrogen atom of the amino group) are coplanar within the limits of 0.039(3) Å. There are eight hydrogen bonds of the O─H…O, N─H…O type in the crystals. Crystal structure obtained for compound I have been compared with the corresponding data for investigated crystalline hydrates bis(citrato)borates of 7-, 8-hydroxy- and 8- and 4-aminoquinolinium cations. X-ray diffraction analysis data allow to elucidate the influence of the mono-substituted quinolinium cations on the complicated crystal structures of bis(citrato)borates crystal hydrates. C21 H25 N2O16B, triclinic: P-1 (No. 2), a = 9.346(2) Å, b = 11.326(3) Å, c = 12.646(3) Å, = 97.46(2)º, = 106.59(2)º, = 101.66(2)º, V = 1231.1(5) Å, Z = 2, ρcalc = 1.544 g/cm3, ρexp = 1.529 g/cm3, R = 0.0449, Rw = 0.0795, T = 293 K.