The natural clam shell (CS) has a unique CaCO3-proteoglycan structure which can be beneficial in improving the strength of materials as a result of the stiff CaCO3 content present in it. Moreover, the existence of active groups such as hydroxyl groups, carboxyl groups, and amino groups in CS can make it possible to form chemical bonds with some functional groups in other materials. In this work, CS which is mostly regarded as waste was utilized to prepare compatible composites via melting process with biodegradable polycaprolactone (PCL). Addition of 15 wt % of polyurethane prepolymer as a compatibilizer to a designed weight ratio of 1 to 1 of CS powder and PCL increased the elongation at break of the composite from 9.3 to 536.5%, and also improved the tensile strength from 14.9 to 18.9 MPa. Particularly important was that scanning electron microscopy investigation revealed that the adhesion between the CS and PCL improved significantly as the content of the compatibilizer was increased. This work shows that CS has great potential applications in the area of compatible composites and could serve as an alternative material for reinforcement in polymer composites