The di- and tri-organotin(IV) complexes of n-butyl hydrogenphthalate and (Z) 3-(4-nitrophenyl)-2-phenyl-2-propenoate were subjected to thermal decomposition by mean of thermogravimetry (TG). The decomposition occurred in steps and the kinetics of every set of reactions was determined using the method described by Coats and Redfern. These results were analyzed to establish the decomposition kinetics and, hence, to calculate the activation energies. The activation energies were also determined by applying the methods described by Horowitz and Metzger, which yielded comparable results. These results confirm that both the ligands act as bidentate in the solid state.