Neonatal thromboembolism is rare and in most cases iatrogenic from indwelling central catheters, peripheral arterial lines, and umbilical lines. It often requires urgent intervention to restore perfusion and to avoid morbidity and even mortality. Very few case reports of neonatal arterial thrombosis at birth are described in the literature. We present the case of a full-term infant noted to have marked left arm swelling at birth. Doppler ultrasound of the arm demonstrated a large thrombus in the left subclavian, axillary, and brachial arteries. He underwent left arm fasciotomy and anticoagulant therapy with good recovery. We present this case with a brief review of the literature.