INTRODUCTION: The intestinal microbiota, comprising trillions of microorganisms primarily bacteria, significantly influences human health and physiology by modulating various biological processes such as nutrient metabolism, immune system regulation, and protection against pathogenic invasion. Dysbiosis, an imbalance in microbiota composition, is associated with a wide range of gastrointestinal disorders, autoimmune diseases, metabolic disorders, and neurological conditions. The microbiota-gut-brain axis represents a bidirectional communication system linking the gut microbiota with the central nervous system, influencing behavior, mood, cognition, and higher-order brain functions. Disruptions in the gut microbiota composition, known as dysbiosis, have been implicated in various neurological and psychiatric disorders, while interventions targeting the gut microbiota have shown promise in ameliorating symptoms of these conditions. OBJETIVE: Analyze and describe the main aspects of role of microbiota in depression and anxiety disorder in the last years. METHODS: This is a narrative review, in which the main aspects of role of microbiota in depression and anxiety disorder in recent years were analyzed included studies in the MEDLINE – PubMed (National Library of Medicine, National Institutes of Health), COCHRANE, EMBASE and Google Scholar databases. RESULTS AND DISCUSSION: The gut microbiota plays a crucial role in modulating neurotransmitter systems such as serotonin, dopamine, gamma-aminobutyric acid (GABA), and glutamate, which are implicated in mood regulation and cognitive function. For instance, gut microbes contribute to serotonin synthesis by metabolizing tryptophan, impacting both local and systemic serotonin levels, thereby affecting mood and mental health. Similarly, emerging evidence suggests that gut microbiota influence dopamine synthesis and metabolism, as well as GABAergic neurotransmission, through various mechanisms. Additionally, gut microbes can modulate glutamate levels, impacting cognition and synaptic plasticity. Dysbiosis of the gut microbiota has been associated with depression and anxiety disorders, characterized by alterations in microbial composition and diversity. Therapeutic interventions targeting the gut microbiota, such as probiotics, prebiotics, and fecal microbiota transplantation, hold promise for alleviating symptoms of mood disorders by restoring microbial balance and modulating neurotransmitter signaling. Understanding the bidirectional communication between the gut microbiota and neurotransmitter systems provides insights into the underlying mechanisms of depression and anxiety disorders and offers novel therapeutic avenues for their treatment and management. CONCLUSION: In summary, the gut microbiota exerts significant influence over neurotransmitter systems crucial for regulating mood, anxiety, and cognitive function, with dysbiosis linked to mood disorders like depression and anxiety. Understanding the bidirectional communication via the gut-brain axis unveils therapeutic potentials of interventions targeting the microbiota, including probiotics, prebiotics, and fecal microbiota transplantation, to improve mental well-being. Environmental factors, stress, and dietary habits also shape gut microbiota, further emphasizing the multifaceted nature of the gut-brain axis in mental health. Future research should delve deeper into this complex interplay to develop personalized interventions for individuals with mood and anxiety disorders.