The aim of this research is to investigate effects of gamma irradiation on antioxidant properties and microbial contaminants in Boletus griseipureus. Samples were ground into powder and later subject to gamma irradiation at 2.5, 5, 7.5 and 10 kGy. The non-irradiated and irradiated samples were then analyzed for their microbial contamination and antioxidant properties such as 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging, ferric reducing antioxidant power (FRAP), total phenolic content, beta glucan content and total triterpenoids. Results showed that microbial contamination decreased with increasing dose. In terms of antioxidant properties, gamma irradiation did not result in significant effects on FRAP, total phenolic content, beta glucan content, and total triterpenoids. However, at 10 kGy of gamma irradiation, DPPH radical scavenging notably increased (p < 0.05).