In the title complex, [Zn(C8H9N2O4)2(H2O)2]·3.5H2O, the ZnII ion is coordinated by two N,O-bidentate H2pimda ligands (H3pimda = 2-propyl-1H-imidazole-4,5-dicarboxylic acid) and two water molecules in a distorted octahedral environment. In the crystal structure, extensive intermolecular O—HO and N—HO hydrogen bonds stabilize the three-dimensional supramolecular network. Intramolecular O—HO hydrogen bonds between the carboxyl groups are also observed. The propyl groups of the two H2pimda ligands are disordered each over two sites, with occupancy factors of 0.752 (5):0.248 (5) and 0.519 (7):0.481 (7). One of the water molecules is half-occupied.