A 75-year-old man was showed wall thickening just below esophagogastric junction(EGJ)by gastroscopy(GS). Biopsy indicated mucinous carcinoma. He was referred to our hospital. Computed tomography(CT), PET-CT showed EGJ cancer and splenic tumor. EGJ cancer was diagnosed GE, Siewert Type Ⅱ, GrePostAnt, Type 1, cT2, cN0, cM0, cStage Ⅰ. The patient underwent total gastrectomy, lower esophagectomy, D2+ #19, 20, 110, 111, 112 lymph nodes dissection, Rou-en- Y reconstruction, distal pancreatectomy, splenectomy, cholecystectomy, and enterostomy. Postoperative complication was pancreatic fistula(Grade Ⅱ). Pathological diagnosis was esophagogastric junction cancer, neuroendocrine carcinoma(NEC), GE, Siewert Type Ⅱ, GrePostAnt, Type 1, pT2(MP), pN1, pM0, pStage ⅡA. Splenic tumor was diagnosed splenic malignant lymphoma, large B-cell, diffuse(DLBCL), NOS, low-immediate risk. Patient was discharged 15 days after the operation and underwent adjuvant chemotherapy with S-1. In this case, he started taking S-1 because the prognosis of NEC is poorer than PSML. There was no evidence of recurrence after 5 months from gastrectomy. As a result of searching for"neuroendocrine tumor"and"malignant lymphoma"in the JAMAS, there was no report of NEC associated with malignant lymphoma. We experienced the rare case of primary splenic malignant lymphoma associated with EGJ NEC. In the case of gastric cancer with splenic tumor, malignant lymphoma of spleen should be concerned.