Breast is a rare location for hydatid cysts, even in endemic regions such as Middle East. They can mimic more common breast pathologies, such as simple cysts, fibroadenomas, or tumors. so, they warrant careful consideration in any patient with a breast lump. Routine evaluations, such as physical examination, ultrasound, and mammography, rarely identify them as the underlying cause, because of similarity of the manifestations. Definitive diagnosis usually made intraoperatively, when surgeons identify daughter cysts or the characteristic laminated membrane, or postoperatively through pathological confirmation. Surgical excision is the main treatment, although microscopic examination of cyst fluid pre-operation can occasionally provide an early diagnostic clue. This report is about a 45-year-old woman from northern Iran, in an endemic area. She'd been feeling a painful lump in her left breast for six months when she showed up at our clinic. Exam turned up a single mass in the upper outer quadrant. Ultrasound and mammogram revealed a cyst full of clear, echo-free fluid, pegged as ACR 2 (BI-RADS category for likely benign). A needle pull showed just white blood cells, polymorphonuclears and lymphocytes, No evidence of malignancy. We proceeded with surgery, and partway through, the cyst ruptured and revealed the laminated membrane. The entire cyst was removed, and pathology confirmed it as a breast hydatid cyst. She recovered well after surgery, and follow-up scans of her liver and chest were clear. We put her on albendazole at 800 mg a day for three months, and a year later, there were no sign of relapse. Breast hydatid cyst is a rare condition, even in endemic areas that hydatid diseases are prevalent. Its presentation can easily be mistaken for simple cysts, fibroadenomas, or malignancies. Recurrence is common after the first drainage. so careful management is very important in endemic regions and physicians should keep parasitic causes in mind. Surgery combined with albendazole is the main treatment and can reduce recurrence risks. other reviews are consistent with this and showed that this treatment has good outcomes, especially when detected early.