Cashew nut shell, a waste product obtained during deshelling of cashew kernels, by past field experience, had been deemed as a fuel unfit for gasification, owing to its high occluded oil content. The oil, a source of natural phenol, oozes upon gasification, thereby making the gasifier throat, downstream equipment, and associated utilities clogged with oil, leading to ineffective gasification and premature failure of utilities because of its inherent corrosive characteristics. To overcome this drawback, the cashew shells were deoiled, by charring them in closed chambers, and were subsequently gasified in an autothermal down-draft gasifier. Stoichiometric and nonstoichiometric (adopting Gibbs free-energy minimization concept) equilibrium modelings were carried out to predict the behavior of the system under varying performance-influencing parameters, viz., equivalence ratio and moisture content. The outcome of the modeling was compared to that of experimental results. The trends of both the models predicting gas composition is observed to be similar; however, the magnitude of composition predicted by them varies, albeit marginally. The developed model satisfies well with the experimental outcome at the equivalence ratio (ER) as applicable to gasification systems, i.e., 0.3-0.4. The sensitivity analyses revealed that (i) the mole fraction of H-2, CO, and CH4 decreases while CO2, N-2, and H2O increases with ER and (ii) H-2, CH4, CO2, N-2, and H2O increases, while CO decreases with the moisture content. The deviation among stoichiometric and nonstoichiometric models, with respect to the experimental outcome, was observed to be at a minimum for H-2 while at a maximum for CO2. The higher heating value (HHV) of the gas predicted by stoichiometric and nonstoichiometric models was observed to deviate from the experimental results by +17.89 and +1.32%, respectively.