Galactorrhea, or nonpuerperal lactation, is a rare complication that can occur after trauma to the chest wall. Although galactorrhea has been reported after thoracic surgery, it has not been previously noted as a potential outcome following cardiac surgery. We present a unique case of hyperprolactinemic galactorrhea experienced by a 39-year-old nongravid female patient after having undergone reoperative mitral valve replacement via a right minithoracotomy. To the best of our knowledge, this is the first reported case of spontaneous lactation occurring after cardiac surgery.