The compound 2-(1-naphthalenylamino)-4-thiazolidinone was synthesized by the reaction of 1-(naphthalene-1-yl)thiourea with ethyl chloroacetate in an ionic liquid, and its structure was characterized by IR, H-1 NMR and single-crystal X-ray diffraction. The crystal of the title compound belongs to monoclinic, space group P2(1)/c with a = 10.0081(3), b = 14.5312(4), c = 7.8739(2) angstrom, beta = 99.425(3)degrees, Z = 4, V = 1129.64(5) angstrom(3), D-c = 1.425 g/cm(3), mu = 0.269 mm(-1), F(000) = 504, the final R = 0.0519 and wR = 0.1507. X-ray analysis indicated that the five-membered ring is essentially planar in this molecule, and intermolecular hydrogen bonds N(1)-H(1)center dot center dot center dot N(2), C(3)-H(3)center dot center dot center dot O(1), C(4)-H(4)center dot center dot center dot O(1) and C(12)-H(12a)center dot center dot center dot O(1) were observed. pi-pi Stacking interactions contribute to the stability of the structure. DSC-TG analysis showed that the title compound experienced a phase change at 190 degrees C and began to decompose above 240 degrees C.