Numerous potential complications are associated with the use of programmable intrathecal drug delivery systems. Radiation is often assumed to cause dysfunctions of the programmable intrathecal device. However, radiation-induced failure of this device and limits of dose exposure were not clinically documented. Here we reported an alarm and failure of an implanted programmable intrathecal pump in a turn-off status exposed directly to radiation used for treatment of a retroperitoneal sarcoma. The radiation induced alarm was likely secondary to the electronic circuit damage and/or battery depletion. Estimated cumulative doses to the pump were in the range of 28.5-36 Gy when the alarm occurred after 20 daily treatments. The intrathecal pump itself exposed to this high-dose radiation did not pose any risk to the patient or the environment. This is the first case description about the pump malfunction secondary to clinical radiotherapy, which is very useful to physicians who manage the pain and radiotherapy for cancer patients.