The physico-chemical studies on terbium laurate in solid state were carried out by IR, X-ray diffrac-tion and thermogravimetric analysis (TGA) measurements. The IR results revealed that fatty acid exist as dimerthrough hydrogen bonding and terbium soaps possess partial ionic character. The X-ray diffraction measurements were used to calculate the long spacings. The decomposition reaction was found kinetically of zero order and value of energy of activation for terbium laurate was found to be in the region of 3.41 to 8.20 K cal mol-1.<