Diffuse large B-cell lymphoma (DLBCL) in the splenic hilar lymph node mimicking an intrasplenic lesion is considered rare in the literature. This case is discussed as a form of a primary splenic DLBCL and as a stage I/II abdominal DLBCL. Primary splenic DLBCL was previously defined as a lymphoma confined to the spleen, with or without involvement of the hilar lymph node or distant lesions. However, the condition is not included in the 5th edition of the World Health Organization classification. In this report, we describe the case of a 63-year-old Japanese male who presented with a 5 cm 18F-fluorodeoxyglucose-avid mass identified on imaging, presumed to be an intrasplenic mass. Subsequent splenectomy confirmed that the mass was DLBCL originating from the splenic hilar lymph node, distinctly separated from the spleen and the tail of the pancreas. Postoperatively, the patient responded well to treatment comprising three courses of a combined regimen of polatuzumab vedotin, rituximab, cyclophosphamide, daunorubicin, and prednisolone. This case underscores the importance of caution when diagnosing intrasplenic lesions based on imaging, as the lesions may be located outside the spleen.