Perioperative radial nerve injury is a rare anesthetic complication, and is rarely seen in association with the use of an automatic blood pressure monitor. As far as we know, only one case has been reported. Here, we report a 26-year-old healthy, lean female who sustained acute radial nerve palsy after appendectomy. A dropped wrist improved 5 days later. The cause of the radial neuropathy is discussed. We recommend that when an automatically cycling blood pressure monitor is used on a lean patient, caution should be taken against such a complication.