Rectal lymphoma is a rare colorectal tumor with incidence of 0.2%-0.6%. We report a rare case of large rectal lymphoma. Our patient is a 48-year-old man, presented with 2 months history of per rectal bleed, altered bowel habits and weight loss. Clinical examination, computed tomography scan and initial endoscopic mucosal biopsy were indistinguishable from Rectal Carcinoma. With high level of suspicion, we resorted to full thickness punch biopsy in lithotomy position for a good tissue sample. Ultimately, an immunohistochemical study confirmed Diffuse Large B-cells Lymphoma (DLBCL). This case highlighted the importance of high level of suspicion for lymphoma when dealing with a rectal tumor. Accurate diagnosis of rectal lymphoma affects the treatment modalities and prognosis of the patient.