Mediastinitis is a serious complication after cardiac surgery. While bacteria are the more common pathogens, fungal infections are rare. Post-operative Aspergillus mediastinitis is considered to be a catastrophic infection, affecting patients with specific predisposing factors undergoing cardiothoracic surgery. The patient outcome after aspergillus mediastinitis is extremely poor despite antifungal therapy and surgery. The diagnosis is usually delayed and relies on direct visualization and culture. Clinical features of post-operative Aspergillus mediastinitis could be minimal, underlining the necessity for a low index of suspicion in cases of culture-negative mediastinitis. Antifungal therapy including amphotericin B or voriconazole along with surgical debridement forms the mainstay of treatment.