Since the operational definition of “cognitive frailty” was first proposed in 2013 by the International Academy of Nutrition and Aging and the International Association of Gerontology and Geriatrics, several studies have been carried out using this cognitive frailty model. In this review, we examined the available clinical and epidemiological evidence for cognitive frailty. Despite its low prevalence (1.0–1.8%) in the community setting, cognitive frailty has been associated with a high risk of disability, poor quality of life, and death; while cognitive frailty appears to be associated with a high risk of dementia, there is no clear evidence for this association. Again, while the prevalence of cognitive frailty appears to have increased in the clinical setting, to date, very few studies evaluated the impact of cognitive frailty. While a new definition of cognitive frailty was proposed in 2015 to incorporate “reversible” and “potential reversible” subtypes, there is a paucity of epidemiological evidence to support this definition. In conclusion, there is no consensus on the definition of cognitive frailty for use in clinical and community settings or on which measures to be used for detecting cognitive impairment. Further study is required to formulate effective preventive strategies for disability in the elderly.