Impar ganglion is a solitary ganglion located retroperitoneally at the end of paravertebral sympathetic chain and usually in front of sacrococcygeal joint. Solitary or metastatic tumour in the surrounding tissues causes poorly localized pain. This case report presents a 75-year old male patient with colon cancer, whose severe pain during defecation could not be controlled with conventional high-dose opioid application but with transcoccygeal radiofrequency thermocoagulation. Radiofrequency thermocoagulation is promising not only for chronic pelvic pain control but also in pelvic pain secondary to malignancy particularly when the ganglion is localized by radiologic imaging techniques.