Silver nanoparticles (AgNPs) were synthesized in situ under gamma radiation environment at room temperature using aqueous silk fibroin (SF) solution obtained from Bombyx mori silk. The formation of the Ag NPs was confirmed by its characteristic surface plasmon resonance (SPR) band at around 424 nm in UV-visible spectra. The strength of the photoluminescence (PL) spectra decreases with increasing dosage reveals the optimum dose required for the synthesis of silver nanoparticles. Dynamic light scattering (DLS) measurement indicated the dose dependent size of the Ag NPs formed in the solution. The transmission electron microscopy (TEM) images showed that the formed nanoparticles are roughly spherical in shape. Further the X-ray diffraction (XRD) analysis confirms the nanocrystalline phase of silver with FCC crystal structure. From this study, it was found that the increasing the radiation dose increases the rate of reduction and decreases the particle size. The size of the Ag NPs can be tuned by controlling the radiation dose.