The thermal degradation characteristics of eucalyptus, pearl millet cob, and corncob were investigated using the nonisothermal thermogravimetric method. This investigation was performed to carry out the thermochemical conversion for obtaining syngas. Thermogravimetric (TG) and differential thermogravimetric (DTG) analyses were carried out to understand thermal devolatilization behavior and estimation of various thermophysical properties of the biomasses. The degradation behavior was analyzed in the light of lignocellulosic composition that was found to have a definitive influence on degradation outcomes. The TG analysis has been utilized to obtain the proximate analysis of biomass. Activation energy using the Flynn-Wall-Ozawa method has been estimated and found to be 201, 150, and 68 kJ/mol for eucalyptus, pearl millet cob, and corncob, respectively. The TG analysis and activation energy together indicated that corncob is easiest for thermochemical conversion among the three biomasses. The TG curve also confirms the same.