We present the case of a healthy 13-year-old female adolescent who developed acute progressive swelling and pain in her right upper extremity that was secondary to an acute deep venous thrombosis of her right subclavian vein. Dynamic imaging revealed subclavian vein compression at the junction of the first rib and proximal third of the clavicle consistent with Paget-Schroetter syndrome, also known as effort-related thrombosis. The compressive etiology of her thrombus was most likely related to her cheerleading activity, in which she served as the pyramid base. The patient received multimodal therapy including anticoagulation, mechanical and site-directed thrombolysis, and a first rib resection. This case illustrates that frontline providers should have a high index of suspicion for an upper extremity thrombosis in pediatric patients who present with unilateral arm swelling.