A 45-year-old woman was presented with a 2-year history of left lower limb claudication symptoms occurring only during long-distance running. Multimodal imaging with exercise duplex ultrasonography and magnetic resonance angiogram confirmed the presence of flow-limiting stenoses in the left external iliac artery consistent with a diagnosis of left external iliac artery endofibrosis. She successfully underwent a left external iliac endarterectomy with vein patch repair and returned to full physical activity soon after. A year following full recovery from her original operation, she presented with similar symptoms on the right side and was managed in a similar manner. This report illustrates an unusual case of bilateral iliac artery endofibrosis occurring in an older endurance runner. We also present a novel diagnostic modality of pre-exercise and postexercise magnetic resonance angiography for iliac endofibrosis.