Bupropion is a synthetic cathinone, which acts therapeutically through norepinephrine and dopamine reuptake inhibition. Recent evidence suggests that serotonin receptor activation occurs with high doses of bupropion and severe serotonin toxicity can occur after isolated bupropion overdoses. Prior observational studies may therefore underestimate the incidence of serotonin toxicity. A retrospective study of patients with bupropion toxicity at a toxicology referral center from 2015-2017 was performed. Patients who overdosed on other serotonergic medications were excluded. Serotonin toxicity was diagnosed retrospectively using Hunter Criteria. Overall, 96 patients were identified with bupropion toxicity. Of these, 18 patients ingested bupropion in the absence of other serotonergic drugs. The incidence of serotonin toxicity was 33% in this population. Serotonin toxicity was more likely after a suicide attempt than those with an accidental ingestion or after recreational drug use. The median dose of bupropion ingested was 2,250 mg in the cohort diagnosed with serotonin syndrome. The incidence of bupropion induced serotonin toxicity is higher than reported. Clinicians should monitor for serotonergic toxicity when evaluating patients after bupropion overdose.