Aging is a heterogeneous process. Most newly diagnosed cancers occur in older adults, and it is important to understand a patient's underlying health status when making treatment decisions. A geriatric assessment provides a detailed evaluation of medical, psychosocial, and functional problems in older patients with cancer. Specifically, it can identify areas of vulnerability, predict survival and toxicity, assist in clinical treatment decisions, and guide interventions in routine oncology practice; however, the uptake is hampered by limitations in both time and resources, as well as by a lack of expert interpretation. In this review, we describe the utility of geriatric assessment by using an illustrative case and provide a practical approach to geriatric assessment in oncology. CASE J.K. is a 73-year-old man who presented to his primary care physician complaining of bright red blood per rectum. He has a medical history of coronary artery disease, hypertension, hyperlipidemia, and cerebrovascular disease. He is on aspirin, lisinopril, metoprolol, and atorvastatin. A subsequent colonoscopy revealed a 3-cm mass in his descending colon. Biopsy of the mass showed invasive adenocarcinoma. He underwent computed tomography scans of the chest, abdomen, and pelvis, which showed no evidence of metastases. A laparoscopic colectomy was performed, and his cancer was staged as T2N2 (stage III) and microsatellite stable. He is referred to you to discuss adjuvant chemotherapy.