OBJECTIVE: The association between work-family conflict and insomnia has not been thoroughly studied. Therefore, we sought to examine the relationship between work-family conflict and insomnia symptoms among Japanese working women. METHODS: In a cross-sectional study, 608 women aged 18-60 years old who worked in aged care services between 2015 and 2016 were selected, and 445 of these women were ultimately included. Insomnia symptoms were measured using the Athens Insomnia Scale. Work-to-family conflict (WFC) and family-to-work conflict (FWC) were assessed through a self-administered questionnaire and were divided into four categories: low work-family conflict (low WFC and FWC), high FWC, high WFC, and high work-family conflict (high WFC and FWC). The prevalence ratio (PR) and 95% confidence interval (CI) of insomnia symptoms were calculated using a Poisson regression model after multivariable adjustment. RESULTS: The multivariable-adjusted PR (95% CI) of insomnia symptoms was 1.99 (1.34-2.93) in the high work-family conflict group compared to the low work-family conflict group. CONCLUSIONS: The results from the present study suggest that insomnia symptoms are highly prevalent among working women in aged care services with high work-family conflict.