Pigment epithelium-derived factor (PEDF), one of the non-inhibitory serpines, is widely expressed throughout the body. Although PEDF was initially identified as a neuronal differentiation factor, more attention has been paid to its anti-angiogenic activity. Additionally, recent researches have demonstrated that PEDF has an anti-tumor effect against several human neoplasms. This review focuses on the pathological role of PEDF in tumors, especially tumor growth and metastasis. PEDF is an endogenous anti-tumor factor and its clinical application seems quite promising, although there is much to be further investigated.