To date, no study has critically reviewed the current literature on the association between magnesium (Mg) and sleep health. Therefore, we carried out a systematic review to assess the association between Mg and sleep patterns in adults' population through observational and interventional studies. We searched for relevant studies through PubMed ( http://www.ncbi.nlm.nih.gov/pubmed ), Scopus ( http://www.scopus.com ), and ISI Web of Science ( http://www.webofscience.com ) from the earliest available date until November 2021. Eligibility criteria for study selection were guided by the following components identified using the PI(E)CO (Population, Intervention (Exposure), Comparison, Outcome) framework: P (adult population), I(E) (high dietary intake or supplementation of Mg), C (low dietary intake of Mg or placebo group), and O (sleep pattern including sleep duration, sleep-onset latency, night awakenings, sleep stages, and sleep phases). The present study involved 7,582 subjects from 9 published cross-sectional, cohort, and RCT systematically reviewed the possible links between Mg and sleep quality (daytime falling asleep, sleepiness, snoring, and sleep duration) in an adult population. Observational studies suggested an association between Mg statuses and sleep quality, while the RCTs reported contradictory findings. This systematic review revealed an association between magnesium status and sleep quality (daytime falling asleep, sleepiness, snoring, and sleep duration) according to the observational studies, while the randomized clinical trials showed an uncertain association between magnesium supplementation and sleep disorders. The association between dietary magnesium and sleep patterns needs well-designed randomized clinical trials with a larger sample size and longer follow-up time (more than 12 weeks) to further clarify the relationship.