Dementia, including Alzheimer’s disease and vascular dementia, is a major public health challenge with significant societal costs. Dietary fatty acids play a crucial role in cognitive function and dementia risk through mechanisms such as neuroinflammation, insulin resistance, and lipid metabolism. This review examines the effects of omega-3 fatty acids, medium- and short-chain saturated fatty acids, and long-chain saturated fatty acids on brain health. Observational studies suggest that EPA, DHA, alpha-linolenic acid, and medium-chain saturated fatty acids may have neuroprotective benefits, while excessive intake of long-chain saturated fatty acids may contribute to cognitive decline. Emerging evidence suggests that short-chain saturated fatty acids may benefit cognitive function. However, findings from randomized controlled trials remain inconsistent. Further research is needed to clarify optimal intake levels and determine the long-term effects of dietary fat composition on cognitive health. Public health efforts should promote culturally sensitive dietary patterns that emphasize dietary fat quality as one potential strategy for mitigating the global burden of dementia.