Rasagiline is a highly potent irreversible monoamine oxidase (MAO)-B inhibitor, antiparkinsonian drug that may be used with caution in patients treated with antidepressant drugs because of the possible appearance of severe adverse effects. It is presented the case report of a woman treated with rasagiline and venlafaxine that presents confusion and a serotonin syndrome. Pathogenesis, physiopathology and treatment are discussed. Growing evidence suggests that Parkinson disease and depression are linked. Antidepressant drugs and PD treatment should be used with caution because of possible drug interaction.