The asymmetric unit of the polyoxidometalate-based organic-inorganic hybrid title compound, (C(3)H(10)NO)(3)[PMo(12)O(40)]·3H(2)O, consists of one α-Keggin-type [PMo(12)O(40)](3-) polyoxido-anion, three independent [CH(3)-O-CH(2)-CH(2)-NH(3)](+) cations and three solvent water mol-ecules. The polyoxidoanion shows characteristic features with respect to bond lengths and angles. In the crystal structure, extensive inter-molecular N-H⋯O and O-H⋯O hydrogen bonding between the organic cations, inorganic anions and solvent water mol-ecules leads to a three-dimensional supra-molecular network.