AIM: The Kihon Checklist is a useful screening tool for assessing frailty in older individuals. However, the clinical significance of the Kihon Checklist in cardiac rehabilitation patients remains unclear. The present study aimed to evaluate the relationship between the Kihon Checklist and the clinical parameters in patients who participated in cardiac rehabilitation. METHODS: We enrolled 845 consecutive patients (584 men, mean age 71 years) who participated in cardiac rehabilitation at Juntendo University Hospital, Tokyo, Japan, between November 2015 and October 2017. The patients were divided into non-frailty (n = 287), pre-frailty (n = 270) and frailty (n = 288) groups according to their Kihon Checklist scores. Cardiopulmonary exercise testing was carried out in 302 patients. RESULTS: The frailty group was older and had a higher prevalence of history of heart failure than the non-frailty group, although left ventricular ejection fraction did not differ significantly between groups. Nutritional index, trunk and limb muscle mass, lean body weight, and grip strength were significantly lower in the frailty and pre-frailty groups than those in the non-frailty group. In the cardiopulmonary exercise test, a stepwise significant decrease in peak oxygen uptake was observed across the three groups (non-frailty 17.2 ± 3.6, pre-frailty 16.0 ± 3.4, frailty 14.4 ± 3.5 mL/kg/min, P < 0.01). Multivariate regression analyses showed that the Kihon Checklist score was significantly and independently associated with peak oxygen uptake (r = -0.34, P < 0.0001). CONCLUSIONS: The Kihon Checklist, which was associated with frailty and exercise tolerance, could be used as a clinical assessment method for patients who participated in cardiac rehabilitation. Geriatr Gerontol Int 2019; 19: 287-292.