Although rare, a hydatid cyst of the breast represents a mammary pseudotumor. We present the case of a 49-year-old woman with no significant medical history, who was diagnosed with an isolated hydatid cyst of the breast confirmed by histopathological examination. This patient consulted for breast asymmetry and a feeling of heaviness in the left breast, with no clinical signs of systemic hydatidosis. The diagnosis was suggested by echo-mammography and confirmed postoperatively by histopathological examination. Although rarely reported, primary hydatid cyst of the breast can cause symptoms that mimic neoplasia. Surgical excision alone proved effective in treating this type of breast cyst.