A unique case of primary pulmonary leiomyosarcoma was diagnosed postmortem in an adult white Carneau pigeon (Columba livia) that had presented with respiratory distress, lethargy, and anorexia nonresponsive to antibiotic treatment. Histologically, the pulmonary mass was composed of multiple interlacing bands of malignant spindle cells. Prominent eosinophilic staining of these cells with Masson trichrome stain and immunohistochemical staining that was positive for actin and desmin confirms smooth muscle origin. This is the first report of a primary pulmonary leiomyosarcoma in a pigeon.