Benzyltrimethylammonium dicitratoborate [C6H5CH2N(CH3)3][(C6H6O7)2B] · H2O (I) has been synthesized and separated out in the form of single crystals for the first time. Its crystal structure has been studied by X-ray diffraction. Crystals are triclinic with a = 10.0832(2) Å, b = 11.1232(3) Å, c = 11.9617(3) Å, α = 84.874(1)°, β = 73.520(1)°, γ = 85.550(1)°, Z = 2, space group P-1. The structure has been solved by direct methods and refined by the full-matrix least-squares technique in the anisotropic approximation up to R = 0.0485 (Bruker-Nonius KappaCCD automatic diffractometer, λMoKα). The crystal structure of compound I is based on centrosymmetric dimers that consist of complex anions and water molecules and linked by the system of hydrogen bonds into a three-dimensional framework. The crystals of compound I contains five asymmetric O-H...O hydrogen bonds.