Cognitive decline, a hallmark of aging, progresses from subtle changes to more significant impairments that may lead to conditions such as mild cognitive impairment and dementia, including Alzheimer’s disease. While genetic predispositions and aging are nonmodifiable risk factors, nearly 45% of dementia cases could be delayed or prevented by addressing modifiable factors like diet, physical activity, and cardiovascular health. This chapter explores the role of nutrition in mitigating cognitive decline, emphasizing dietary patterns (Mediterranean and MIND diets, overall diet quality), key food groups, and nutrients (e.g., B vitamins, vitamin D, and omega-3 fatty acids). With aging populations on the rise and no definitive treatments for dementia, dietary interventions hold significant promise for enhancing brain health and reducing the global burden of cognitive disorders.