Synchronous double malignancies of gastric carcinoma (GC) and malignant lymphoma (ML) are rare and very difficult to treat. We report a case of synchronous GC and nodal ML, regarding which clinical and pathological features and treatment are discussed. A 68-year-old woman with a history of inguinal hernia was admitted for abdominal pain and high fever and subsequently underwent herniorrhaphy, but the fever remained. Computerized tomography showed a stomach mass and multiple enlarged lymph nodes in the abdominal cavity and inguinal regions. Gastric adenocarcinoma coexistent with advanced in situ follicular lymphoma was confirmed by endoscopy, biopsy of inguinal lymph nodes and bone marrow examination. Two chemotherapy regimens, R-CHOP (rituximab, cyclophosphamide, perarubicin, vincristine and prednisone) and systemic therapy (5-fluorouracil and calcium folinate) combined with regional perfusion (oxaliplatin and etoposide) through the left gastric artery were performed at intervals against ML and GC, respectively. Partial remission in both tumors was achieved after 4 courses of treatment, but the patient finally died of heart failure. Scrupulous biopsy of non-draining lymph nodes in patients with gastrointestinal carcinomas is supposed to improve the diagnostic rate of simultaneous nodal ML. The interval chemotherapy strategy with two independent regimens is beneficial for such patients, especially for those unable to tolerate major surgery.