In the present work, various blend ratios of poly (lactic acid) (PLA), triallylisocyanurate (TAIC) and octavinyl-POSS (OvPOSS) were prepared by melt compounding in an Xplore microcompounder and molded by an Xplore microinjection molding device. POSS is a new generation organic/inorganic hybrid nanoparticle having possibility to improve the performance of polymers without sacrificing mechanical and thermal properties. TAIC and OvPOSS were used as crosslinking agents. After the compounding process, PLA, PLA/TAIC and PLA/OvPOSS composites were exposed to a gamma irradiation at various adsorbed doses ranging from 0 to 100 kGy. The properties of neat PLA, PLA/TAIC and PLA/OvPOSS composites were investigated using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA) and tensile testing. Results showed that both chain scission reactions and formation of network structure occurred simultaneously after gamma irradiation. The highest gel formation was obtained from PLA composites including 3 wt% OvPOSS at the dose of 100 kGy. DSC results indicated that a sharp decrease in the degree of crystallinity (X-c%) of PLA in the presence of TAIC and OvPOSS was obtained after gamma irradiation process. All irradiated composites exhibited lower elongation at break and higher E-Modulus values at any irradiation doses. TGA results showed that irradiated samples were more thermally stable than the unirradiated ones. Moreover, the heat deflection temperature (HDT) of PLA in the presence of TAX and OvPOSS was found higher than that of neat PLA. Brittle surface morphology of composites after gamma irradiation process was obtained from SEM analysis.