Pulmonary mucormycosis and aspergillosis with disseminated mucormycosis involving gastrointestinalin is a very rare but lethal infection leading to extreme mortality. Herein, we present a unique case of pulmonary coinfection with Cunninghamella bertholletiae and Aspergillus flavus, with disseminated mucormycosis involving the jejunum caused by C. bertholletiae in an acute B-lymphocytic leukemia (B-ALL) patient with familial diabetes. Early administration of active antifungal agents at optimal doses and complete resection of all infected tissues led to improved therapeutic outcomes.