Frailty is a geriatric syndrome with increased risk for poor health outcomes, including falls, cognitive impairment, hospitalization, and mortality. In previous studies, associations between frailty and sleep-related factors or sleep disorders have been investigated. We examined the relationship between frailty and insomnia, which are both common condition in older adults. Hormonal changes with aging and/or lifestyle changes all affect sleep physiology, which are vulnerable to the risk of insomnia. As the severity of frailty decreases the quality of sleep, and the long/short sleep duration is related to the risk of frailty, it can be assumed that frailty and sleep are reciprocally related. The association between frailty and insomnia has been variously proven in epidemiological studies conducted around the world. A close evaluation of insomnia and frailty in older adults provides a basis for improving the health of people in the aged society. There are few related studies in Korea, and in the future, not only basic epidemiological studies but also studies explaining the psychoneuroendocrinological mechanism of the relationship between insomnia and frailty should be performed together.