The present report describes the first known, case of a pseudoaneurysm of the perforating branch of the deep femoral artery following anterior cruciate ligament (ACL) reconstruction. A 19-year-old man underwent ACL reconstruction using the outside-in femoral tunnel-creation method. Seven days after the surgery, he complained of abnormal thigh pain and had swelling with local heat on the distal lateral thigh. Magnetic resonance imaging, computed tomography, and color Doppler ultrasonography showed the pseudoaneurysm in the thigh. Resection surgery was successfully performed by a vascular surgeon 12 days after ACL reconstruction. Careful examination and awareness of postoperative symptoms such as thigh pain and swelling after ACL reconstruction were critical for the early diagnosis of pseudoaneurysm.