Sheets made from untreated and treated wood and bagasse pulps were subjected to thermal degradation in static air and monitored by the differential thermal analysis (DTA) technique. Percent of resin (resol or novolac) added to the pulps was chosen on the basis that maximum breaking length was achieved. The DTA profiles were obtained and analyzed using the Prout-Tompkins law. A computer program was developed to elucidate the appropriate order of reaction (n) and, consequently, the thermodynamic parameters. Infrared spectra of the samples, and their relation with the mechanical properties and the above thermodynamic parameters, were elucidated. It was found that resin addition (either novolvac or resol) to bagasse pulp led to increased thermal stability, mean hydrogen strength, and crystallinity index. In addition, the stretching vibration corresponding to OH groups was shifted to a lower wavenumber due to its bonding with the phenolic resin. However, no significant changes were observed (specially thermal stability) in the case of sheets made from treated wood pulp.