Research on the effects of polyunsaturated fatty acids on children's sleep has made significant advancements. This study explores the unique pathways through which polyunsaturated fatty acids, particularly docosahexaenoic acid and eicosapentaenoic acid from the n-3 series, influence sleep regulation in children. Neurobiologically, docosahexaenoic acid and eicosapentaenoic acid have been shown to bi-directionally modulate neurotransmitters and circadian rhythms via the gut-brain axis, reshaping gut microbiota and affecting brain signaling. In terms of inflammation and immune regulation, this study is the first to confirm that Maresin1, produced from n-3 fatty acids, can inhibit the activation of specific inflammasomes, thereby mitigating the disruptive effects of pro-inflammatory cytokines on sleep. The analysis of clinical applications indicates that newly developed medium- and long-chain triglyceride formulations rich in docosahexaenoic acid exhibit excellent digestive absorption in infants' gastrointestinal systems, paving the way for new products designed to enhance infant sleep. However, current research has limitations concerning the precise dosing of docosahexaenoic acid, the representativeness of samples, and the overall rigor of study designs. Mechanistically, polyunsaturated fatty acids may exert their effects through various pathways, including neurobiology, inflammation, immune regulation, and endocrine modulation. In clinical studies, different formulations of fish oil show varying safety profiles and bioavailability. Future research should prioritize high-quality studies to clarify how different doses of polyunsaturated fatty acids affect children's sleep, assess long-term safety, and investigate interactions with other factors, ultimately providing solid theoretical and practical guidance for improving children's sleep.