Lymphedema is characterized by a defect in the lymphatic system that causes limb swelling. Impaired uptake and transport of lymphatic fluid through lymphatic vessels causes accumulation of protein-rich fluid in the interstitial spaces, which leads to swelling of the limb. Primary lymphedema often presents at birth. The rare cases that arise after age 35 years are described as lymphedema tarda. The great majority of patients with lymphedema have swelling of the lower limbs-upper limb lymphedema is a rare disorder. An 84-year-old woman presented with a 3-year history of unilateral swelling of the right upper limb. There were no constitutional symptoms and no evidence of lymphadenopathy or systemic disease. Blood tests, carcinoembryonic antigen test, computed tomography scans, and venous Doppler ultrasound were all normal. The diagnosis was primary upper limb lymphedema. The swelling that occurs in upper limb lymphedema is permanent and usually extends to the hand. About one-third of patients with this condition also present with lower limb lymphedema. Thorough investigations are warranted in cases of unilateral upper limb lymphedema to rule out occult malignancy and systemic disease.