We report of the occurrence of an incidental retrograde left internal jugular venous (IJV) catheterization during a right external jugular vein (EJV) approach. After induction of anesthesia, central venous catheterization was performed through the right EJV using the standard technique. There was no expected cardiac arrhythmia during guide wire insertion, and there was no atrial waveform on the CVP tracing. Therefore, we took a chest X-ray for confirmation of catheter placement, which revealed the tip was placed in the left IJV. We withdrew the catheter about 6-7 cm to prevent possible impairment of cerebral venous drainage by a retrograde-positioned catheter in the IJV. We think that the dilation of the left IJV due to Trendelenburg position, positive pressure ventilation, and the upward direction of the J-wire tip contributed to the contralateral retrograde IJV catheterization. We recommend that a chest X-ray always be taken if correct catheter tip placement is not confirmed during CVP catheterization.