External iliac artery endofibrosis describes an intimal subendothelial fibrosis leading to wall thickening and stenosis that has been described in high-performance athletes. There are anatomical, mechanical, and probably metabolic factors that may contribute to this pathology. Ankle-brachial index (ABI) measurement with exercise testing, duplex ultrasound, computed tomography (CT) or magnetic resonance (MR) angiogram, and ultimately arteriography help to make the diagnosis. Management can be conservative, but most cases require surgical intervention. External iliac vein stenosis and thrombosis in cyclists has rarely been described in the literature. We report a case of extensive left lower limb deep venous thrombosis (DVT) including the external iliac vein diagnosed in a 57-year-old athletic cyclist with a history of external iliac artery thrombosis.