Background: Unrepaired dextro-transposition of great arteries (D-TGA) is well known for long-term complications, including tricuspid valve regurgitation, arrhythmias, and coronary artery abnormalities. Pulmonary hypertension (PH) is a frequent, progressive, and fatal complication in unrepaired CHD. This chronic condition can induce pulmonary thromboembolism (PTE). Aim: To report the management of PTE in unrepaired D-TGA with PH. Case Presentation: We present a rare case of an eleven-year-old male in unrepaired D-TGA with PH. He came with hemoptysis with no sign of acute or chronic infection. This condition was not associated with endocarditis or tuberculosis. The patient underwent a CT-pulmonary angiography examination and found a filling defect in the apical and posterior branches of the right superior pulmonary artery, suggesting a PTE that caused pulmonary parenchymal infarction. He was treated with intravenous low molecular weight heparin (LMWH) for ten days (1 mg/kg) and tranexamic acid. On follow-up, he did not experience cardiovascular collapse or hypotension; by the day, the hemoptysis had decreased in frequency and volume. He received long-term warfarin (2 mg/day) for three months. After three months of follow-up, the PTE was not visualized from CT-pulmonary angiography. Summary: Hemoptysis is rare and life-threatening in unrepaired CHD. Heparin administration continued with warfarin, and tranexamic acid provides a good prognosis in patients with PTE with D-TGA and PH.