Impairment of oral health has a negative impact on the quality of life (QOL) of the elderly. Activities of daily living (ADL) are known to be an important determinant of their QOL. A controlled study was conducted between September and November 2007 to determine the effects of dental treatments on the QOL and ADL among 30 institutionalized Japanese elderly who were allocated into two groups, an intervention group and a control group. Their mean age was 80+/-9 years. Outcome data were collected 6 weeks after baseline in both groups. QOL and ADL were assessed using General Oral Health Assessment Index (GOHAI) and Functional Independence Measure (FIM). The intervention group, which had received dental treatment, showed significant increases in GOHAI scores between baseline and 6 weeks (p=0.04), whereas no significant difference was found between baseline and 6 weeks in the control group. The differences in the changes in the FIM scores for expression were significant in the model adjusted for covariables (p=0.03). Our findings showed that dental treatments increased the oral health-related QOL and the expression function in the ADL. Promoting dental care service at nursing facilities may be beneficial for maintaining the residents' QOL.