Given the heterogeneous conditions of older people with cancer, decisions can be challenging, and treatment should be individualized. Comprehensive geriatric assessment (CGA) is a process of examination and intervention establishment that aims to inform the individualization of cancer treatment and concomitant health conditions in older adults. The objective of this chapter is to summarize what a comprehensive geriatric assessment is, what evidence there is of its use in cancer patients, the barriers to its widespread use, and what scales and questionnaires are recommended as part of the assessment. CGA has been found to modify treatment intention, reduce chemotherapy toxicity, increase treatment completion, and identify health conditions that can be improved with interventions. CGA can be time-consuming, and its use still has barriers to implementation, including provider’s lack of knowledge. In the last years, several trials have been published that support its use. The American Society of Clinical Oncology (ASCO) recommends a CGA in older adults with cancer as part of their care that includes assessment of comorbidity, non-cancer survival, function and mobility, cognitions, fall risk, depression, and chemotherapy toxicity. The most common methods of assessing these domains are described. With the advent of more older adult patients with cancer, dissemination on the use of comprehensive geriatric is of utmost importance to be able to provide the best care for this population group in a way holistic and personalized.