We present a 61-year-old male with FLT3-mutated acute myeloid leukemia treated with midostaurin who developed acute kidney injury requiring hemodialysis and pulmonary renal syndrome. Antibodies to proteinase-3, myeloperoxidase, and glomerular basement membrane were negative. Renal biopsy confirmed acute pauci-immune focal necrotizing glomerulonephritis (GN) with fibrin crescents indicating rapidly progressing glomerulonephritis. He improved with pulse methylprednisolone, intravenous cyclophosphamide, and plasma exchange with resolution of hemoptysis. This case highlights the importance of prompt renal biopsy to guide early initiation of life-saving therapies. To our knowledge, this is the first reported case of ANCA-negative pauci-immune necrotizing GN likely secondary to midostaurin.