To improve the care of older adults with cancer, the traditional approach to clinical trial design needs to be reconsidered. Older adults are underrepresented in clinical trials with limited or no information on geriatric-specific factors, such as cognition or comorbidities. To address this knowledge gap and increase relevance of therapeutic clinical trial results to the real-life population, integration of aspects relevant to older adults is needed in oncology clinical trials. Geriatric assessment (GA) is a multidimensional tool comprising validated measures assessing specific health domains that are more frequently affected in older adults, including aspects related to physical function, comorbidity, medication use (polypharmacy), cognitive and psychological status, social support, and nutritional status. There are several mechanisms for incorporating either the full GA or specific GA measures into oncology therapeutic clinical trials to contribute to the overarching goal of the trial. Mechanisms include utilizing GA measures to better characterize the trial population, define trial eligibility, allocate treatment receipt within the context of the trial, develop predictive models for treatment outcomes, guide supportive care strategies, personalize care delivery, and assess longitudinal changes in GA domains. The objective of this manuscript is to review how GA measures can contribute to the overall goal of a clinical trial, to provide a framework to guide the selection and integration of GA measures into clinical trial design, and ultimately enable accrual of older adults to clinical trials by facilitating the design of trials tailored to older adults treated in clinical practice.