We present herein the case of a patient with brachial plexopathy, the first manifestation of giant cell arteritis (GCA). A 71-year-old woman presented with a subacute-onset weakness of her upper extremities; the patient had an initially good clinical response to steroid treatment. However, a few weeks after steroid discontinuation, she manifested fever and fatigue and increased serum markers consistent with a systemic inflammatory response. A PET-CT scan revealed an increased uptake in the subclavian arteries and a temporal biopsy was typical for GCA. Oral administration of high dosage steroids improved the patient's clinical symptoms and normalised her inflammatory serum markers.