Pain is prevalent among patients with cancer who are being treated with radiotherapy. However, the prevalence of pain varies across regions, and pain management is affected by several factors. This cross-sectional study aims to determine the prevalence of pain, assess the adequacy of pain management and identify factors affecting pain in patients undergoing radiotherapy. A total of 94 patients were included in the study. The prevalence of pain was determined through the Brief Pain Inventory tool, while the adequacy of pain management was assessed through the Pain Management Index. Demographic, clinical and treatment-related factors were obtained and analysed for association with the presence of pain and the adequacy of pain management. Of the 94 patients, 59 (62.8%) experienced pain while 35 (47.2%) did not. The mean pain intensity score of patients was 3.6 (standard deviation: 2.3). Most patients (67.8%) experienced mild pain with low pain interference (67.8%) on daily functions. Of the 59 patients who experienced pain, 34 (57.6%) had inadequate pain relief while 25 (42.2%) had adequate pain control. Being admitted at the hospital during radiotherapy was significantly associated with adequate pain relief. Use of analgesic was also significantly associated with pain management, with a higher rate of weak and strong opioid use in those with adequately treated pain. In this single-institution study, the prevalence of pain was high. Pain management was inadequate in more than half of the patients experiencing pain. A disparity in the prescription of analgesics, particularly opioids, was observed. Patients with inadequate pain management were less likely to receive opioids, which likely reflects the presence of several barriers that limit its access to patients.