Objectives: This study examined the relations among 5 personality factors, self-regulatory efficacy and subjective well-being in parents with developmental disabilities. This study also examined the mediating effect of self-regulatory efficacy on the relationship between 5 personality factors and subjective well-being in parents with developmental disabilities. Methods: The research subjects consisted of 114 parents with developmental disabilities. They completed questionnaires 5 personality factors, self-regulatory efficacy and subjective well-being by parents. The data were analyzed by SPSS 22.0 program. Results: The results of this study showed that 5 personality factors–neuroticism and extroversion–had a direct effect on subjective well-being in parents with developmental disabilities. Second, 5 personality factors-extroversion- had an indirect effect on the subjective well-being through self-regulatory efficacy in parents with developmental disabilities. Conclusions: These findings have implications for future research and practice by highlighting the importance of self-regulatory efficacy in subjective well-being in parents with developmental disabilities.