Tianeptine is an atypical mu-opioid receptor agonist. It is available as an antidepressant outside the United States, but it is also classified as a controlled substance in many other countries. It is not approved by the United States Food and Drug Administration for the treatment of depression but it can be obtained online without a prescription. The case described in this article involved a patient who developed symptoms of psychosis on supratherapeutic doses of tianeptine, highlighting the importance of inquiring into all supplements taken by patients when conducting an initial psychiatric evaluation.