<h3>Purpose</h3> Pulmonary mucormycosis accounts for ∼2% of fungal infections in lung transplant recipients (LTR). Delays in diagnosis and limited treatment options contribute to high mortality rates of 50-70% in local infections, and as high as 95% in disseminated infections seen in immunocompromised patients. We present a case of invasive mucormycosis of the native lung post-single lung transplant (LTx). <h3>Methods</h3> 61 y.o. M presented 5 months post-right single (LTx) with DKA, shortness of breath, and left-sided infiltrates on chest radiograph. CT chest showed cavitary lesions in native lung concerning for fungal infection while on prophylactic posaconazole. TBBx was consistent with mucormycosis. Treatment was initiated with systemic and inhaled antifungal therapies: inhaled liposomal amphotericin B (L-AmB), IV L-AmB and IV isavuconazonium sulfate (isavuconazole). Serial chest CTs showed worsening necrotizing infection despite medical therapy. Patient underwent left upper lobectomy, with pathology confirming invasive mucormycosis. He continued oral isavuconazole upon dischargeDHD, however was re-admitted 3 months post-lobectomy with fever, lethargy, and CT chest showing central cavitation in native left lower lobe. Bronchoscopy revealed fungating endobronchial mass completely obstructing the left lower lobe, consistent with mucormycosis (Figure 1A). <h3>Results</h3> Patient discharged on multi-agent regimen with plan to complete 6-month course of IV L-AmB, followed by lifelong oral isavuconazole and inhaled L-AmB. Subsequent TBBx without evidence of mucormycosis. <h3>Conclusion</h3> Delays in diagnosis and treatment of mucormycosis is life-threatening, especially in the native lung after single LTx. Patient likely failed oral isavuconazole monotherapy due to decreased blood supply to native lung after single LTx. Inhaled antifungals in conjunction with early surgical intervention should be considered along with standard medical management for LTR with mucormycosis.