Self-determination is an absolute right that can be applied to any human being. On the other hand, discussions on self-determination in the field of developmental disabilities are very divided because people with developmental disabilities are recognized as beings in need of care and protection rather than independent beings. Nevertheless, promoting self-determination of people with developmental disabilities can help them understand their identity and form an adaptive attitude as a valuable person, which can ultimately improve their quality of life. Therefore, this study aims to verify the mediating effect of acceptance of disability in the relationship between self-determination of people with developmental disabilities and quality of life. To this end, 484 people with developmental disabilities were selected for analysis using the 3rd (2020) data of the disability and life dynamics panel as the most recent data established by the Korea Disabled People’s Development Institute, and bootstrapping using Process Macro for SPSS The method was applied to verify the mediating effect. The analysis results are summarized as follows. First, the self-determination of people with developmental disabilities has a positive (+) effect on the quality of life. Second, self-determination of persons with developmental disabilities had a positive (+) effect on acceptance of disabilities. Finally, acceptance of disability showed a partial mediating effect in the relationship between self-determination and quality of life of people with developmental disabilities. Based on these results, this study intends to suggest practical and policy implications for improving self-determination and acceptance of disabilities for people with developmental disabilities.