In the title compound, [Mn(C(12)H(9)O(2))(2)(C(7)H(6)N(2))(2)]·H(2)O, the Mn(II) ion is located on a twofold rotation axis and six-coordinated, displaying a distorted MnN(2)O(4) octa-hedral geometry. The crystal packing is stabilized by N-H⋯O hydrogen bonds, which give rise to a one-dimensional structure along [001], and π-π inter-actions between the imidazole rings and between the benzene rings of the 2-(naphthalen-1-yl)acetate ligands [centroid-centroid distances = 3.761 (3) and 3.728 (4) Å]. The contribution of the electron density associated with the disordered water molecules was not considerd in the final structure model.