Takayasu arteritis (TA) is a large-vessel vasculitis characterised by stenosis, dilation and/or aneurysm formation. We present a case of a 43-year-old man with an initial manifestation of an acute thrombosed aneurysm. He was found to have a thrombosed right common femoral artery aneurysm on Doppler ultrasound. Physical examinations revealed a substantial difference in blood pressure level between bilateral upper extremities, and absent pulses at right upper and lower extremities. The diagnosis was confirmed by angiography, which revealed 100% occlusion of the right common femoral artery. Biopsy of the thrombosed aneurysm was consistent with a diffuse lymphocytic subendothelial infiltrate. The patient was treated with high-dose corticosteroids and had a good response to treatment, as demonstrated by a decrease in sedimentation rate, and recovery of the right side pulses. This case helps to create awareness among physicians that TA may present with an acute occlusion of an aneurysm without the typical warning symptoms of TA.