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Metabolic bariatric surgery induces significant anatomical and physiological changes in the gastrointestinal tract that may substantially affect the pharmacokinetics of orally administered drugs. These changes include, among others, reduced gastric volume, increased gastric pH, bypass of absorption segments in the small intestine, alterations in drug metabolism, as well as rapid weight loss and changes in body composition. Many neuropsychiatric medications are characterized by a narrow therapeutic window; therefore, the effects of metabolic bariatric surgery may lead either to reduced drug absorption and therapeutic failure or, conversely, to increased drug levels with a risk of toxicity. Interindividual variability is considerable, making it difficult to predict pharmacokinetic responses in individual patients. This review presents the impact of metabolic bariatric surgery on commonly used neuropsychiatric medications, aiming to promote safe and optimal pharmacotherapy in this population. The article includes a literature review, recommendations for therapeutic drug monitoring, and guidance for clinical and laboratory follow-up. Given the complexity of this issue, a proactive approach is recommended, including assessment of drug levels prior to surgery and close monitoring in the early postoperative period until clinical and laboratory stability is achieved, followed by periodic monitoring based on drug characteristics, patient factors, and the specific surgical procedure performed. A multidisciplinary approach involving a neurologist and/or psychiatrist, along with a clinical pharmacist, is essential to optimize neuropsychiatric treatment in patients undergoing metabolic bariatric surgery.