In the title compound, [Ni(C13H17N3)2]Cl2·3.5H2O, the geom-etry of the NiN6 complex cation is slightly distorted octa-hedral, with a facial arrangement of the two tridentate N-[2-(di--methyl-amino)-eth-yl]quinolin-8-amine ligands around the metal ion. The asymmetric unit consists of two independent complex half-mol-ecules located on centres of inversion, together with two chloride counter-anions and 3.5 water mol-ecules of solvation, one of which is disordered across an inversion centre. In the crystal, O-H⋯O, O-H⋯Cl and N-H⋯Cl hydrogen-bonding inter-actions form a three-dimensional network structure.