The purpose of this study was to evaluate the effects of a 12-week group-based body-weight squat training program on muscle mass, muscle strength, and balance in physically frail community-dwelling older men and women. Fifteen older adults (mean age =78.7 yr) who needed assistance performing activities of daily living (ADL) according to long-term care insurance regulations in Japan participated in the study. Participants performed squat exercise in a group-setting using body-weight as resistance while singing for one set consisting of 48 reps twice weekly for 12 weeks. Body mass, thigh girth, thigh muscle thickness assessed by B-mode ultrasound, knee extension torque (KET), static and dynamic balance (static (SB): sway velocity (SV) standing on firm or foam surfaces with eyes open or closed; dynamic (DB): limits of stability) were measured before and after the intervention. Following the intervention, participants significantly (P<0.05) decreased body mass and increased KET relative to body mass. Although thigh girth did not change, thigh muscle thickness did increase. There were no appreciable changes in DB nor in SB, except SV standing on a firm surface with the eyes open improved. Group-based body-weight squat exercise in physically frail older adults improves muscle mass and strength but has little effect on balance parameters.