The asymmetric unit of the title compound, C₈H₂₂N₂ ²⁺·2C₇H₆NO₂ ⁻·2.25H₂O, consists of half each of two centrosymmetric tetramethylbutane-1,4-diammonium cations, two p-aminobenzoate anions and 2.25 solvent water molecules. As a characteristic feature of 4-aminocarboxylic acid, twisting of the carboxylate group from the aromatic plane is observed in the p-aminobenzoate anions. Other noteworthy features are the `head-to-tail' chain and the formation of dimers through N—H...O and O—H...O hydrogen bonds involving amino groups, carboxylate groups and water molecules. Futhermore, an intricate three-dimensional hydrogen-bonding network involving N—H...O and O—H...O is observed.