It is widely accepted in clinical practice that chronological age is a poor predictor of treatment tolerance and outcomes in older adults with cancer. Intrinsic vulnerability is more a function of underlying frailty, rather than chronological age. Frailty is a state of increased vulnerability to stressors, such as cancer and its treatment, which can lead to adverse health outcomes for patients. Capturing this heterogeneity in reserve capacity is the cornerstone of management in geriatricmedicine, but remains poorly understood or adopted in radiation oncology. A two-step approach, using a shorter screening tool, followed by full assessment for those who need it, is the mostresourceful way of implementing frailty assessment in radiotherapy departments. It is important for radiation oncology professionals to identify frailty and to use this information in multidisciplinary decision making in order to develop a personalised radiotherapy approach for the older person. There are many ways we can effectively use this information, such as considering treatment fractionation schedules that would limit the burden of travel for those with social frailty, or reviewing the range of modalities at our disposal, which might limit toxicity in the older person at high risk of deterioration during treatment. Frailty assessment is not carried out in many radiotherapy departments presently, but there are many international models to use as exemplars as to how it may be implemented in clinical practice. There are many opportunities for further research and role development in this field at the current time.