Failure of a double-lumen endotracheal tube (DLT) to isolate the lung during thoracic surgery can have significant consequences. In this report, we examine an approach for rescuing a malpositioned DLT. A 37F left-sided DLT was inserted and its proper position confirmed. After positioning, repeat confirmation of position and the ability to achieve 1-lung ventilation were performed, but inadequate isolation of the lung being operated on was noted after incision. A 7-Fr Arndt bronchial blocker was positioned through the tracheal lumen of the DLT to obtain 1-lung ventilation. This technique can be used to rescue a malfunctioning DLT without the need for extubating and reintubating the trachea.