Intradiscal electrothermal therapy (IDET) is a minimally invasive procedure that alleviates chronic discogenic pain by delivering controlled heat to modify collagen and destroy pain-conducting nerve endings. While IDET offers a less invasive alternative to surgery, it carries risks such as nerve damage, infection, vertebral osteonecrosis, and, rarely, spinal cord injury. This report presents the case of a 36-year-old woman who developed left-sided hemiparesis following IDET for cervical disc herniation at the C5/6 level. Magnetic resonance imaging revealed cervical cord edema, and examination revealed neurological deficits, including reduced proprioception, motor strength, and senses of pain and temperature. Anterior cervical discectomy and fusion led to thermal injury on the left ventral spinal cord, and postoperative recovery resulted in significant neurological improvement, although some sensory deficits persisted. This case underscores the importance of appropriate patient selection and meticulous procedural technique to prevent severe complications, emphasizing the importance to reserve IDET for specific cases and to consider alternatives for more complex spinal conditions.