Thermal behavior of untreated and treated bagasse-pith with acidic and basic dyes was investigated using differential thermal analysis (DTA) and thermogravimetric thermal analysis (TGA). The results showed that the thermal decomposition pattern can be divided into three peaks. The first peak is endothermic while the second and the third peaks are exothermic. The peak intensities and the corresponding temperatures were different for the untreated acid treated materials. The decomposition thermographs of the reacted acid dye differ than that of basic dye; this is due to the differences in adsorption behavior and differences in the adsorption capacity of each dye toward bagasse. The reaction rate, activation energy, entropy change, enthalpy change and Gibbs free energy for the treated and untreated bagasse-pith were calculated. The calorific values of the treated pith are higher than untreated.