A 47-year-old man presented with epiphora and a mass around the lacrimal sac in his left eye. Imaging studies revealed a favorable diagnosis of sinusitis-related mucocele. However, the pathological study of the excised tumor demonstrated a diffuse large B cell lymphoma. The patient was consequently referred to the oncology department for further management. Malignant lymphomas of the lacrimal sac are rare and they can mimic mucoceles. As such, they should be included in the list of differential diagnoses for lacrimal sac mass.