Proptosis is commonly encountered in clinical practice. We report on a patient with acute proptosis, eyelid swelling, and chemosis, which was initially treated as cellulitis. After radiological and pathological assessments, a diagnosis of large B-cell lymphoma was made. The patient died within 2 months of presentation. Not all patients with proptosis have cellulitis. Proptosis, especially unilateral proptosis, should always lead to a radiological scan in case of malignancy.