Mechanical robustness of polymer solar cells should be ensured for the device reliability, but the brittle active layers of fullerene derivative based polymer solar cells would fracture easily causing the device failure. Therefore, mechanical properties of polymer solar cells should be investigated thoroughly in order to enhance the mechanical reliability. Herein, the mechanical properties of polymer solar cells were examined depending on the acceptor types (polymer or small molecule acceptors) and the content. In addition, the fracture behaviors were revealed in detail with various morphology analyses. This result demonstrates the importance of polymer acceptors to improve the mechanically robustness of polymer solar cells.