Thromboembolic events incidence is low in pediatrics; high suspicion and explicit management algorithms are essential. We present a 12-year-old female patient with two weeks of dyspnea, orthopnea, and ankle edema. Tests showed metabolic acidosis, hyperlactatemia, elevated D-dimer, and positive SARS-CoV-2 CRP. The echocardiogram showed severe right ventricular dysfunction and supra-systemic pulmonary hypertension. Chest CT angiography showed extensive bilateral pulmonary thromboembolism. Anticoagulant therapy was started. She presented with hemodynamic instability. Adrenaline, norepinephrine, milrinone, and nitric oxide were started. The clinical picture was extremely severe in the first 24 hours. It was decided to perform systemic thrombolysis with alteplase, which led to an improvement. Cardiorespiratory stabilization and anticoagulation are the mainstays of therapy in massive pulmonary thromboembolism. Fibrinolytic therapy is used in selected high-risk cases. In this patient, systemic reperfusion therapy with alteplase was performed with no significant complications.