Interdigitating dendritic cell sarcoma (IDCS) is an extremely rare malignancy derived from antigen-presenting cells, with 55 cases reported thus far. A standard treatment modality is still being debated. This report describes a 56-year-old female who presented with right tonsillar enlargement and right submandibular swelling for 6 months. Treatment with empiric antibiotics did not result in improvement of her symptoms. Fine needle aspiration of the tonsil revealed no malignant cells. Tonsillectomy was eventually performed due to persistent symptoms. Based on microscopic findings, immunohistochemical stains, and review of the literature, the present case was finally diagnosed as IDCS of the tonsil with cervical lymph node involvement. The patient received four cycles of CHOP (cyclophosphamide, doxorubicin, vincristine and prednisone) chemotherapy, and a clinically complete response was achieved followed by adjuvant radiation.