Objectives: A prospective study was conducted to assess factors associated with risk of turnover among care workers in group homes (GHs) for elderly individuals with dementia. Methods: In January, 2010, 51 out of 238 GHs in Sapporo City responded to our request for participation in a survey. During February and March of 2010, 438 out of 700 care workers (62.6%) in the GHs returned a completed questionnaire to us. They were followed up with until March of 2012, and 395 subjects (90.1%) responded to our survey, which was conducted twice. Over the course of 2 years, 91 subjects left their jobs. Cox's proportional hazards model was used for analysis, adjusting for gender and age. Results: Less provision of social support by supervisors, colleagues, family or friends was significantly associated with increased risk of turnover. Financial aids for off-the-job training was marginally significantly associated with reduced risk of turnover. Longer duration of working for frail elderly care was significantly associated with decreased risk of turnover. Habitual smoking was significantly associated with increased risk of turnover. Conclusions: Social support in the workplace may be important to reduce the risk of turnover in care workers at GHs. Further prospective studies are required in other areas in Japan.(J Occup Health 2013; 55: 487–494)