This systematic review explores the relationship between the gut microbiota, metabolic syndrome (MetS), and sleep disorders. The review highlights 36 articles that associate gut microbial signatures with MetS or sleep disorders, focusing on studies evaluating dietary patterns, dietary supplementation, and probiotics. The gut-brain axis, which connects the gut microbiota and sleep regulation pathways, is identified as a key mediator in this complex interaction. The review emphasizes the role of dietary choices in promoting or impairing both MetS and sleep homeostasis through microbial composition and metabolites. Key findings include the common microbial signature associated with sleep disturbances and MetS, characterized by a decrease in butyrate producers and an enrichment in the Bacteroidetes phylum. The review also discusses the potential benefits of healthy dietary patterns and fiber supplementation in modulating gut microbiota and improving metabolic and sleep parameters. Finally, the review suggests that further observational and mechanistic studies are needed to confirm and validate these findings.This systematic review explores the relationship between the gut microbiota, metabolic syndrome (MetS), and sleep disorders. The review highlights 36 articles that associate gut microbial signatures with MetS or sleep disorders, focusing on studies evaluating dietary patterns, dietary supplementation, and probiotics. The gut-brain axis, which connects the gut microbiota and sleep regulation pathways, is identified as a key mediator in this complex interaction. The review emphasizes the role of dietary choices in promoting or impairing both MetS and sleep homeostasis through microbial composition and metabolites. Key findings include the common microbial signature associated with sleep disturbances and MetS, characterized by a decrease in butyrate producers and an enrichment in the Bacteroidetes phylum. The review also discusses the potential benefits of healthy dietary patterns and fiber supplementation in modulating gut microbiota and improving metabolic and sleep parameters. Finally, the review suggests that further observational and mechanistic studies are needed to confirm and validate these findings.