Polylactic acid (PLA)/silk fibroin (FS) composite has been used in industry and biomedicine for the past two decades due to its biodegradability and biocompatibility, with an emphasis on tissue engineering. In this work, PLA/FS composites with different content of FS were prepared and the effect of SF on the properties of PLA was investigated. PLA/ SF composites were prepared with different weight content of SF via melt mixing in a laboratory Brabender mixer. Techniques used for the characterization of PLA/SF composites are: differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), contact angle measurement and swelling. Results obtained with DSC technique showed that with addition of SF, melting temperature decreases, while crystallization temperature increases. The addition of SF increased the degree of crystallinity because of the nucleation effect of SF. Thermal stability of PLA/SF composites in the nitrogen and air atmosphere decreased with addition of SF. Results obtained with DMA technique showed that composites with a higher SF content have a higher storage modulus at 25 °C. The glass transition temperature is slightly lower compared to the neat PLA. The contact angle measurements confirm that in composites with a higher SF content dispersed contributions decrease while polar contributions increases. The swelling test revealed that composites with a higher SF content are more hydrophilic.