Purpose: Many patients with advanced cancer receive primary supports from informal caregivers (IC). As patient health deteriorates, IC assume increasing responsibility, often accompanied by distress. We investigated the quality of life (QOL) of IC of patients referred to a palliative radiotherapy (PRT) program. Methods: IC accompanying patients to a dedicated PRT clinic completed a survey based on the validated Caregiver Quality of Life Index-Cancer (CQOLC). Demographics, burden, and engagement in support services were evaluated. Summary statistics were calculated, and parameters were assessed for association with CQOLC scores by a generalized linear model. Results: Two hundred one surveys were analyzed representing 197 unique patients. The mean age was 68.3 years, with predominantly lung (25.0%) and prostate (19.3%) malignancies. 24.4% had been in hospital/long-term care within the previous 7 days. IC were 60.8% female, and 60.6% were the patient’s spouse. 69.5% lived with the patient and 38.3% were additionally employed. IC spent a daily mean of 6.6 h (SD 7) assisting with instrumental (72.5%) and basic (37.5%) activities of daily living. Mean CQOLC score was 82.1/140 (SD 20). 63.8% of IC had previously accessed support service(s), most commonly home care (37.2%) and pharmacy (29.1%). 55.9% indicated interest in services not yet accessed. Multivariate analysis revealed additional employment, cohabitation, poor patient performance status, and interest in accessing more support services significantly correlated with higher IC burden. Conclusions: Employing the CQOLC to screen IC of patients referred to a PRT program permits early identification of vulnerable IC to facilitate linkage with appropriate supports.