The title coordination polymer, {[Nd(2)(C(4)H(2)O(4))(3)(H(2)O)(4)]·3H(2)O}, was synthesized by the reaction of neodymium(III) nitrate hexa-hydrate with fumaric acid in a water-methanol (7:3) solution. The asymmetric unit comprises two Nd(3+) cations, three fumarate dianions (L(2-)), four aqua ligands and three uncoordinated water mol-ecules. The carboxyl-ate groups of the fumarate dianions exhibit different coordination modes. In one fumarate dianion, two carboxyl-ate groups chelate two Nd(3+) cations, while one of the O atoms is coordinated to another Nd(3+) cation. Another fumarate dianion bridges three Nd(3+) cations: one of the carboxyl-ate groups chelates one Nd(3+) cation, while the other carboxyl-ate group bridges two Nd(3+) cations in a monodentate mode. The third fumarate dianion bridges four Nd(3+) cations, where one of the carboxyl-ate groups chelates one Nd(3+) cation and coordinates in a monodentate mode to a second Nd(3+), while the second carboxyl-ate groups bridges two Nd(3+) cations in a monodentate mode and one O atom is coordinated to one Nd(3+) cation. The Nd(3+) cations are in a distorted tricapped-trigonal prismatic environment and coordinated by seven O atoms from the fumarate ligands and two O atoms from water mol-ecules. The Nd(3+) cations are linked by two carboxyl-ate O atoms and two carboxyl-ate groups, generating infinite Nd-O chains to form a three-dimensional framework. There are O-H⋯O and C-H⋯O hydrogen-bonding interactions between the coordin-ated and uncoordinated water mol-ecules and carboxyl-ate O atoms.