Henoch Schönlein purpura (HSP), also known as IgA vasculitis (IgAV), is a systemic small-vessel vasculitis that predominantly affects adolescents and is rare in adults. In many cases, the onset of HSP has been causally linked to an infectious disease. We encountered a case of HSP with severe renal involvement diagnosed by renal biopsy following bacillus Calmette-Guerin (BCG) therapy for bladder cancer. This is of clinical relevance, as intravesical BCG administration is becoming an established therapy for superficial bladder cancer and is supposed to be safe. It is important for all clinicians to recognize that BCG therapy has this rare but potentially serious systemic complication.