Mental health conditions have been linked closely to an imbalance of microbiota in the gut, leading to disruption of the microbiome (dysbiosis). Several neurotransmitters, such as GABA (gamma-aminobutyric acid), serotonin, and glutamate, are produced in the gut, which are associated with anxiety and depressive symptoms. Mental health and the gut have been linked closely, and many mental illnesses have been associated with gut dysbiosis. Probiotics are marketed to improve gut health, act as mood enhancers, and be effective in reducing stress as unregulated over-the-counter supplements. Given healthcare disparities and patient-doctor gaps across the globe, this review aims to appraise the literature on probiotics for the prevention and treatment of mental disorders. PubMed and Google Scholar databases were searched till March 2023 using the MeSH words “prebiotics,” “probiotics,” “synbiotics,” and “psychobiotics.” Out of 207 studies, 26 studies met the inclusion criteria and were included in the review. Studies suggest probiotics could be an effective and economical adjunct therapy; however, due to weak study design and low power, the results are inconclusive. Their use is not without risks, and healthcare providers need close supervision until more robust longitudinal studies are conducted to appraise their efficacy and safety profiles.