Physical activity and physical fitness are important for health, functional mobility and performance of everyday activities. To date, little attention has been given to physical activity and physical fitness among nursing home residents with cognitive impairment. Therefore, the main aim of this study was to examine physical activity behavior and physical fitness of institutionalized older adults with cognitive impairment and to investigate their interrelations. Forty-eight older adults with cognitive impairment (83.9 ± 7.7 years; 72.9% women) and 22 without cognitive impairment (82.2 ± 8.8 years; 54.5% women) participated. Physical activity was objectively assessed with accelerometers and physical fitness components (muscular strength, flexibility, balance, body composition and reaction time) were evaluated with physical fitness field tests. Nursing home residents with cognitive impairment spent only ˜ 1 min per day in moderate physical activity and ˜ 89 min in light physical activity. In average they accumulated 863 (± 599) steps per day and spent 87.2% of the accelerometer wear time in sedentary behavior. Participants’ physical fitness components were markedly low and according to the cut-offs used for interpreting the results a great number of nursing home residents had an increased risk of associated health problems, functional impairment and of falling. The performance in some physical fitness tests was positively associated with physical activity. Participants without cognitive impairment had higher levels of physical activity and physical fitness than their counterparts with cognitive impairment. These results indicate that nursing home residents, especially those with cognitive impairment, have low levels of physical activity, spent a high proportion of daytime in sedentary behavior and have low physical fitness. Nursing homes should implement health promotion strategies targeting physical activity and physical fitness of their residents.