Studies were carried out to evaluate the influence of microwave pre-treatment on the thermal decomposition of different lignocellulosic biomass pellets and on the yield of volatile compounds. Microwave pre-treatment of biomass pellets was performed using a 700 W heat capacity microwave oven by varying the mw irradiation time of biomass pellets along with estimation of the effect of mw pre-treatment on the mass density and elemental composition of pellets responsible for changes of the thermal decomposition and yield of volatiles during the gasification of pre-treated pellets. Experimental studies of the thermal decomposition of pre-treated biomass pellets and formation of volatile compounds (CO, H2, CxHy) were conducted using a laboratory-scale setup with the heat capacity 5 kW which combines a biomass gasifier and a combustor. The results of the complex study allow to conclude that the microwave pre-treatment of biomass pellets promotes an increase of the weight loss rate by decreasing the mass density, but increasing the surface area and reactivity of the pre-treated pellets thus activating the thermal decomposition during the gasification of the pre-treated pellets with a faster and enhanced yield of combustible volatiles. The results of the experimental study suggest that mw pre-treatment of lignocellulosic pellets can be used as a tool to control the thermal decomposition of lignocellulosic pellets and the yield of combustible volatiles.