Polydatin (PD) is a major chemical component of Polygonum cuspidatum and it could also be found in a variety of other sources. PD is a polyphenol belonging to the chemical family of stilbenoids. Previous studies have shown that PD exhibits many pharmacological activities, including cardioprotective, neuroprotective, and antioxidative activities. With vascular dementia (VaD) rat models, PD markedly attenuated cognitive deficits. Biochemical analysis revealed that PD decreased the production of malondialdehyde (MDA) and significantly increased superoxide dismutase and catalase activities. Additionally, PD effectively alleviated the injuries of cultured neurons induced by oxygen–glucose deprivation. The therapeutic potential of PD for VaD seems related to its antioxidative activity and the direct protection of neurons. Furthermore, PD could also effectively inhibit the polymerization of amyloid-β peptides, which is a major mark in the progression of pathogenesis in Alzheimer’s disease (AD). These results suggest that PD is a promising drug candidate or nutraceutical for the treatment of VaD and AD