In this work, the effects of treatment of tetra-needle-shaped zinc oxide whisker (T-ZnOw) on the mechanical properties and morphology structure of polycarbonate (PC) and PC/T-ZnOw composites were investigated by mechanical property test, scanning electron microscope (SEM), Fourier transform infrared (FTIR), and X-ray diffraction (XRD) analysis. The results show that untreated T-ZnOw seriously deteriorates the mechanical properties of PC, especially the impact strength due to the weak interfacial adhesion and poor compatibility between PC matrix and T-ZnOw.However, YoungÂÂs Modulus of the composites with untreated or treated T-ZnOw gradually increases with increasing the content of the whiskers. Compared with the composites filled with untreated T-ZnOw, the treatment of T-ZnOw could remarkably improve the tensile and impact strength of PC/T-ZnOw composites due to the enhanced interfacial adhesion between polymer matrix and the whiskers. No new absorption peak is detected by FTIR. The results of XRD patterns show that T-ZnOw has little effect on the crystalline behaviors of PC, which indicates PC/T-ZnOw composites consist of two phase structures.