The effects of nucleating agent, temperature of crystallization, and degree of machine direction (MD) orientation on the mechanical, optical, and thermal properties of biaxially oriented polypropylene (BOPP) films were investigated. Addition of nucleating agent improved only the initial tear resistance in the MD; however, the other mechanical and optical properties did not change appreciably. Ln the set of experiments in which the crystallization temperature was increased, the degree of crystallinity also increased. Thus, Young's modulus, yield stress, and tensile strength increased in both directions with higher degree of crystallinity. The yield strain did not change significantly, but the strain at break was higher. Although the initial tear resistance was smaller in both directions with increasing crystallization temperature, the tear propagation resistance did not change. In this case, haze and diffuse transmittance were slightly higher, but the total transmittance was constant. In the set of experiments in which the machine direction orientation was increased, the degree of crystallinity also became higher. Owing to the effects of higher crystallinity and higher MD orientation, the modulus, yield stress, and tensile strength increased, but the yield strain and tear propagation resistance did not significantly change in both directions.