Background: Mediastinal echinococcosis (hydatid disease) is a rare manifestation of Echinococcus granulosus infection, accounting for less than 0.1% of all hydatid cyst locations. Its presentation may mimic other mediastinal masses, posing diagnostic and therapeutic challenges. Case Presentation: A 22-year-old female presented with chest pain for eight days, headache for four days, vomiting and diarrhoea for two days, and fever for three days. She had a prior history of a cystic lesion in the anterior mediastinum, confirmed on biopsy as Echinococcus granulosus. High-resolution CT thorax revealed a well-defined hypodense lesion in the prevascular region with thin internal septations and air pockets, closely abutting the manubrium sternum and pulmonary trunk. The patient underwent median sternotomy with complete excision of the cystic lesion. Intraoperatively, the lesion was encapsulated and removed intact to prevent spillage. Post-operative recovery was uneventful. Conclusion: Primary mediastinal hydatid cysts are uncommon and should be considered in the differential diagnosis of cystic mediastinal masses, especially in endemic regions. Complete surgical excision remains the treatment of choice, supported by anti-helminthic therapy to prevent recurrence.