Stability studies and kinetics of β-1,3-glucanase from Trichoderma harzianum NCIM 1185 are reported. The critical parameters, pH and temperature, affecting the stability of β-1,3-glucanase were optimized using response surface methodology. The optimal combination of pH and temperature were 3.6 and 41 °C, respectively. The stability of β-1,3-glucanase was studied at various conditions of pH and temperature above the optimal conditions. Since the final activity was not zero, a non-first order deactivation model was used to explain the experimental data. Enzyme kinetic studies were carried out with and without inhibitors. Cu²⁺ behaved as a noncompetitive–uncompetitive mixed inhibitor, whereas EDTA and NH₄⁺ behaved as competitive–noncompetitive type mixed inhibitors during the hydrolysis of β-1,3-glucan.