Non-Hodgkin lymphoma (NHL) is the 11th most common cancer worldwide and the 4th most common pediatric cancer. The GI tract is the most common extranodal site of NHL, making up about 30-40% of extranodal cases. The median age at diagnosis for gastrointestinal NHL (gNHL) is around 61. On the other hand, gNHL is very rare in the pediatric population. Herein, we report the case of a 15-year-old girl who complained of abdominal pain and vomiting after meals, with severe B symptoms (fever, night chills, and severe weight loss). Esophagogastroduodenoscopy showed a mass in the lesser curvature of the stomach. Subsequent biopsy and immunostaining of the sample confirmed the diagnosis of diffuse large B-cell lymphoma. CT and PET-CT scans indicated the involvement of mesenteric and lesser omental lymph nodes. Later on, the patient started an R-CHOP chemotherapy regimen. In this report, we aim to shine the light on such a rare disease in this age group.