An airway-exchange catheter (AEC) can increase the safety of exchanges of endotracheal tubes (ETTs); however, the procedure is associated with potential risks. We describe a case of esophageal misplacement of a single-lumen ETT after switching from a double-lumen tube, despite the use of an AEC as a guidewire. To avoid this, physicians should consider the insertion depth and maintenance depth of the AEC and should verify its position before changing ETTs and should perform, if possible, with simultaneous visualization of the glottis with direct or video laryngoscopy during the exchange. Additionally, the new ETT position should be confirmed by auscultation, end-tidal carbon dioxide, and portable chest X-ray.