The development of reliable, environmentally friendly processes for the synthesis of noble metal nanoparticles is an important aspect of nanotechnology today. One such approach that shows immense potential is based on the in situ synthesis of silver nanoparticles (AgNPs) using a natural biological material such as aqueous silk fibroin (SF) solution obtained from Bombyx mori silk. In the present study, the SF/AgNPs colloidal solution were prepared by in situ reducing AgNO 3 with SF at room temperature under white light without any reducing agent. The SF/AgNPs composite films were prepared by solution casting method and were characterised by UV-visible (UV-vis) spectroscopy, Fourier transform infrared spectroscopy, photoluminescence and transmission electron microscope (TEM) techniques. The UV-vis spectroscopy revealed the formation of AgNPs by showing a typical surface plasmon resonance band at 412 nm from the UV-vis spectrum. The TEM images show that formed nanoparticles are roughly spherical and of uniform particle size, and the average particle size is 16 nm.