Abstract: Immune checkpoint inhibitors can induce a rare but fatal complication known as hemophagocytic lymphohistiocytosis(HLH). However, reports of ICI-related HLH in breast cancer are extremely limited, and no cases induced by the combination of toripalimab with chemotherapy have been documented. This article reports a case of a breast cancer patient who developed persistent high fever 13 days after receiving toripalimab combined with chemotherapy. Diagnostic evaluations met the HLH-2004 diagnostic criteria. Following methylprednisolone pulse therapy, the patient's symptoms improved rapidly, with subsequent consolidation treatment involving low-dose etoposide. Follow-up examinations one month after discharge showed normal results. This case suggests that toripalimab may induce HLH in breast cancer patients and that initial treatment with glucocorticoids alone can be effective. It provides a reference for the early clinical identification and management of such severe immune-related adverse events.