The Cd atom in the hydrated title salt, (C7H11N2)2[CdBr4]·H2O, exists in an approximately tetrahedral coordination geometry, with Br—Cd—Br angles in the range 105.52 (3)–111.50 (3)°. The cation, anion and water molecule interact by O—H⋯Br, N—H⋯Br and N—H⋯O hydrogen bonds, forming a linear chain structure running along the a axis.