A 64-year-old man with interstitial pulmonary fibrosis and a small patent foramen ovale with right-to-left shunting underwent bilateral lung transplant without closure of the patent foramen ovale. Postoperatively, the patient remained persistently hypoxemic with partial response to high-flow oxygen. Investigations revealed the presence of a large patent foramen ovale with right-to-left shunting on echocardiography and a shunt fraction of 21% on cardiac catheterization. Two months after the lung transplantation, primary surgical repair of the patent foramen ovale was performed with immediate improvement in oxygenation. Three years postoperatively, the patient remained oxygen independent.