In recent years, there has been a growing interest in the improving effects of natural antioxidant compounds in dementia-associated diseases, including Alzheimer's disease, Parkinson's, and others. In this chapter, we highlight the most important natural antioxidants used in dementia. Main attention is given to polyphenol compounds such as resveratrol, ginkgolides, curcumin, or genistein, for they are the most studied antioxidants. We also mention the growing importance of caffeine and the carbazole alkaloids from Murraya koenigii in the reduction of cognitive deficit in neurodegenerative pathologies. We explore the main features of these compounds and downstream signaling pathways in the reduction of oxidative stress anomalies or the inhibition in the formation of amyloid peptides in the brain. Finally, we review other prospective compounds and mention the ongoing clinical trials in humans.