BACKGROUND: Mucormycosis, commonly known as the "black fungus," is a severe infection affecting multiple organ systems, including the skin, brain, lungs, and gastrointestinal tract. This case report is focused on pulmonary mucormycosis, which is frequently observed in organ transplant recipients. Diagnostic challenges arise from nonspecific symptoms. CASE PRESENTATION: Our case involved a 61-year-old male with a history of renal transplantation. The patient initially presented with a persistent cough and bloody sputum and was treated unsuccessfully for a presumed fungal infection. A lung biopsy confirmed pulmonary mucormycosis, emphasizing the heightened vulnerability of immunocompromised individuals. CONCLUSION: This case highlights the intricate nature of mucormycosis diagnosis and management, particularly in post-organ transplantation patients. It underscores the importance of awareness and collaboration among medical specialists, including infectious disease experts, pulmonologists, and transplant teams, to optimize outcomes in the face of this life-threatening infection.