This review focuses on understanding the vital role of the mTOR signaling pathway in the pathology of various neurodegenerative diseases (NDs), such as Alzheimer’s (AD), amyotrophic lateral sclerosis (ALA), Huntington’s disease (HD), and Parkinson’s (PD); and discusses the application of omega-3 polyunsaturated fatty acids (PUFAs) as mTOR inhibitors and as potential treatments for various NDs. Omega-3 PUFAs play a central role in maintaining cerebral functions and brain development; these omega-3 PUFAs also exert significant protective effects against inflammatory damage within the brain. Recent evidence reported that omega-3 PUFAs can act as mTOR inhibitors—which mitigate the cognitive impairment brought about by NDs. Furthermore, several components of mTOR signaling have been identified as culprits in the progression of several NDs. Encouraging data from experiments have provided significant evidence for the relationship between the mTOR signaling pathway and NDs, and mTOR inhibitors have been proven to effectively ameliorate the cognitive deficits brought about by NDs in a number of animal models. Hence, omega-3 PUFAs are a potential treatment for NDs.