Objectives: Older patients with cancer present many symptoms during treatment. One of those symptoms is fatigue, which may be caused by factors unrelated to cancer. One of those factors is frailty increased with age. Frailty and fatigue affect older patients with cancer physically, psychosocially, emotionally, and spiritually. This study investigated the relationship between frailty and fatigue in older patients with cancer. Data Sources: This descriptive study was conducted between July 15, 2019, and February 15, 2020, in the medical oncology polyclinic and the medical oncology outpatient treatment unit of a university hospital. The sample consisted of voluntary 288 patients who met inclusion criteria. Data were collected using a demographic questionnaire and the Edmonton Frail Scale (EFS), and the Cancer Fatigue Scale (CFS). Conclusion: The mean age of participants was 71.71 +/- 5.29 years. Participants had a mean EFS score of 6 +/- 3.21. Of participants, 36.1% were not frail, while 20.1% were vulnerable, 19.1% moderately frail, 17.7% mildly frail, and 6.9% severely frail. Participants had a mean CFS score of 21.41 +/- 12.25. There was a positive correlation between EFS and CFS scores (P = .000, r = 0.734). Of participants, 63.8% were frail with physical and cognitive fatigue. The higher the frailty, the higher the fatigue. Implications for Nursing Practice: Elderly patients with cancer appear to be fragile, with frailty causing fatigue and many other conditions. It is important to determine the frailty and fatigue of elderly patients with cancer. It is essential understand the relationship between the frailty and fatigue for effective and correct management of nursing care. (c) 2021 Elsevier Inc. All rights reserved.