BACKGROUND: Pyoderma gangrenosum (PG) is a rare neutrophilic dermatosis characterized by rapidly progressive ulcers. PG manifests clinically as painful ulcers with undetermined violaceous borders. A case of diffuse large B-cell lymphoma with cutaneous involvement treated with chimeric antigen receptor T-cell (CAR T-cell) therapy with subsequent development of PG is presented. CASE REPORT: Based on her clinical presentation, the patient was started on a prednisone taper with wound vacuum. Complete granulation and 90% reepithelialization were noted at 3-month follow-up. The wound was fully resolved within 4 months, without subsequent reactions. CONCLUSION: The relationship between CAR T-cell therapy and PG remains unknown. In this case, excellent response was achieved using standard treatment for PG wounds, which included prednisone taper and appropriate wound care. The discovery of novel cutaneous manifestations resulting from immunotherapy treatment remains essential for targeted therapy and further management of post-radiation site reactions. More research is needed to determine the significance of CAR T-cell therapy on post-treatment reactions, including PG.