The possibility of using beech wood sawdust and hazelnut husk waste generated during the cultivation of Pleurotus ostreatus mushrooms as a filler in polycaprolactone (PCL)-based biocomposite films was investigated. Chemical and physical properties of the PCL biocomposites were determined. The beech sawdust and hazelnut husk were exposed to degradation for 73 d and 78 d, respectively, in slightly acidic environments at a relative humidity of 75%. The degraded materials caused the holocellulose and lignin contents in the PCL biocomposites to decrease, while the cellulose and α-cellulose contents increased. In general, as the lignocellulosic waste content increased, the tensile strength (TS) and elongation at break (EatB) values decreased and the tensile modulus (TM) and water absorption (WA) values increased. It was determined that the PCL biocomposite with the degraded beech sawdust absorbed more water than the composite with the undegraded beech sawdust. On the other hand, the PCL biocomposite with the degraded hazelnut husk absorbed less water than the composite with the raw hazelnut husk.