Rare complications of using the internal jugular vein for vascular access are related to puncture of neighboring organs or other structures. We report the atypical case of a 55-years-old woman with unilateral diaphragm paralysis attributed to accidental damage of the phrenic nerve during an attempt to canalize the internal jugular vein. Other more common causes were ruled out. The severe restrictive ventilatory changes produced had only minor clinical and gasometric repercussions, as previous function was normal and no acute or chronic respiratory disease was present. When ventilation is already compromised, however, this event could seriously worsen the patient's condition.