Anti-glomerular basement membrane (anti-GBM) disease is characterized by linear deposition of immunoglobulin G (IgG) along the GBM. The concurrence of anti-GBM disease with another type of glomerulonephritis has been well described. We report a case of necrotizing glomerulonephritis in association with prodromal systemic symptoms, deterioration in kidney function less rapid than expected, and the presence of circulating anti-GBM antibody. This was initially diagnosed histologically as immunoglobulin A (IgA) nephropathy based on immunohistochemistry (IHC) staining, but immunofluorescence (IF) staining on a subsequent biopsy was more consistent with a diagnosis of anti-GBM disease with coexisting mild IgA nephropathy. Prompt initiation of standard treatment of anti-GBM disease normalized kidney function. This case highlights that anti-GBM disease can present atypically and may also co-exist with another form of glomerulonephritis.