The fracture behavior of polypropylene/carbon fiber composites with different interfacial adhesion was evaluated using the essential work of fracture method. All samples exhibited ductile fracture characteristics, while the specific essential fracture work, w_e, was obviously decreased by carbon fiber incorporation, indicating the impaired ductility and toughness for polypropylene. The cracks were easily formed and expanded at the fiber‐matrix interface under external force for polypropylene/original carbon fiber composites, since the weak interfacial adhesion between the fiber and matrix could not prevent the generation of new crack. Introduction of compatibilizer as well as surface modification of fibers effectively improved the interfacial adhesion between the fiber and matrix, so that the value of w_e increased and the elastic deformation of the composites became more prominent. Therefore, the improvement of interfacial adhesion between the fiber and matrix influenced both elastic and plastic deformation of the composites.