Lay abstract The elderly population is increasing rapidly worldwide, and most cancer patients are over the age of 65. In this age group, preexisting medical conditions other than cancer lead to the use of multiple drugs, which is defined as polypharmacy. Additionally, the anticholinergic burden (ACB) of the drugs affects cancer treatment in the elderly. This study investigated the frequency of polypharmacy and ACB in elderly patients with and without cancer and their relationship with geriatric syndromes such as depression, falls, nutritional and cognitive impairments. We found that ACB was higher in older patients without cancer than those with cancer and is related to increased falls, depressive symptoms, and impaired nutritional and functional status in older patients. Given the prevalence of cancer among older adults, it is crucial to understand the potential effects of the ACB for rational drug use and optimum cancer management in older patients with cancer.