A 70-year-old woman was referred to our department because of a solitary nodular shadow, 2 cm in diameter, in the right mid zone on a chest X-ray. Chest computed tomography revealed a pulmonary arteriovenous fistula (PAVF) in S4 of the right lung. Although the patient did not present with PAVF-related symptoms or hypoxemia, in view of the threat of serious complications, a therapeutic decision was made for coil embolization of the pulmonary artery feeding the PAVF. During the endovascular embolization procedure, the coil migrated into the mitral valve chordae tendinae. Urgent thoracotomy was therefore performed and the coil was safely retrieved from the site. Via the same thoracotomy incision, the PAVF with its surrounding tissue was also resected from the right lobe of the lung. The inadvertent coil migration in this patient may be explained by the fact that the fistula was not large enough to allow the coil to stay in place for the prevention of blood flow from the feeding vessel. These findings indicate that surgical resection of PAVF should be selected when the size of the fistula is too small for coil embolization. Otherwise, if transcatheter embolization is preferred, the detachable balloon approach may be appropriate.