Carbon fiber reinforced thermoplastic composites have attracted a lot attention due to their short molding times and recycling. Polypropylene (PP) is widely used for matrix materials. However, PP has weak adhesion with reinforcing fibers because of its low surface free energy, and it is difficult to impregnate into dry fiber due to high viscosity at the melted phase. In this study, carbon fiber surface treatment such as silane coupling agents and plasma treatment were performed to enhance the interfacial strength between the carbon fibers and PP. The treated carbon fiber surfaces were characterized by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and single filament tensile test. The interlaminar shear strength (ILSS) of composites with respect to surface treatment method was determined by the three points bending test. In this test results, the ILSS of the silane coupling agent treated specimens after plasma treatment increased by 48.7% compared to that of untreated specimen.