The title compound, C20H32N82+·2Br−·3H2O, was obtained by the reaction of 1,3,5,7-triazatricyclo[3.3.1.13,7]decane with 1,3-bis(bromomethyl)benzene in acetonitrile. The asymmetric unit contains a unique 1,1'-(benzene-1,3-diyldimethanediyl)bis(3,5,7-triaza-1-azoniatricyclo[3.3.1.13,7]decane)dication, two bromide anions and three water molecules. The 3,5,7-triaza-1-azoniatricyclo[3.3.1.13,7]decane (C6N4H12)+ moieties lie on the same side of the molecule, and the pseudo torsion angle (H12N4C6)—CH2…CH2—(C6N4H12) is −5.25 (18)°. The molecular dication C20H32N8+ is charge-balanced by a pair of crystallographically independent halide hydrate clusters, and the cation and clusters are interlinked by C—H…O and C—H…Br hydrogen bonds. The Hirshfeld surface analysis and fingerprint plots reveal that the packing in compound 2 is directed mainly by H…H (56.7%) and H…Br/Br…H (21.3%) contacts. The thermal analysis showed between 30 and 180 °C the gradual loss of three water molecules, which represents the loss of one and two crystalline water molecules from the two types of clusters, respectively. A second noticeable weight loss between 180 and 230 °C is observed, depictive of the thermal decomposition of the dication of the title compound.