The aim of this study was to determine the associations of older assisted living residents' tooth brushing habits with health and nutritional status. We assessed the tooth brushing habits, nutritional status, oral health, use of dental services, and morbidity of 1,447 assisted living residents in the Helsinki metropolitan area of Finland. Of the residents, 17% did not clean or had not cleaned their teeth and/or dentures daily. Those not cleaning their teeth and/or dentures daily were more often male, less educated and had a mean length of stay in assisted living longer than those who cleaned their teeth and/or dentures daily. They were more often malnourished and dependent in ADLs. In addition they more often had poorer oral health and used fewer dental services. Poor tooth brushing habits indicate poor oral and subjective health. More attention should focus on the oral hygiene of frail older assisted living residents.