The asymmetric unit of the title compound, 2C18H12O4·C2H6OS·2H2O, consists of four crystallographically independent mol-ecules of 5-(naphthalen-1-yl)isophthalic acid, two dimethyl sulfoxide and four water mol-ecules. The dihedral angles formed by the the planes of the aromatic fragments of the organic mol-ecules range from 57.4 (1) to 59.1 (1)°. In the crystal, multiple O-H⋯O hydrogen bonds link the water mol-ecules with the carbonyl and sulfoxide groups, giving rise to double ribbons along the b-axis direction.