Background: Alzheimer's disese is the most frequent cause of dementia and is one of important cause of mortality and morbidity in the world. Although, there are different therapeutic options for its treatment , the results of these therapies are disappointing. Omega-3 fatty acids in marine- derived food products, affect on different mechanisms, improve cognitive function, memory.in this study, effect Omega-3 fatty acids in marine- derived food products of cognitive disorders and Alzheimer's are reviewed. Methods: The method employed in this research was a systematic bibiliographic review,in which only the double-blind placebo-controlled studies or the clinically detailed enough open-labeled studies using validated scales were retained. Results: Many studies have shown that Omega-3 fatty acids in marine- derived food products, affect by different mechanisms include decrease inflammation and oxidative stress, synaptogenesis, synaptic plasticity, and neurogenesis promotion in neuroprotection and improvement cognitive function and memory, also omega3 fatty acid could lead to a decrease in risk of Alzheimer's diseas and the other cognitive impairements. Conclusion: However, more and large clinical trials are needed to confirm the beneficial effects of omega 3 fatty acid supplementation on the management of Alzheimer's disease and cognitive decline.