Chimeric antigen receptor (CAR) T cells targeting CD19 have changed the treatment landscape of patients with relapsed/refractory diffuse large B-cell lymphoma. Infections are one of the most frequent complications after CAR T-cell therapy. Most of these infections are bacterial, although viral infections can also occur in this setting. Adenovirus-induced hemorrhagic cystitis is a rare infectious complication and is usually observed after bone marrow or solid organ transplantation. Herein we report a case of adenovirus-induced hemorrhagic cystitis in a patient experiencing urinary symptoms within the first month after CAR T-cell infusion. Based on our experience and a literature review, we discuss the diagnostic approach and potential treatment options for this infrequent infection after CAR T-cell therapy.