The current aging service industry has problems in meeting the ever-increasing demand for the home-based elderly care service (HECS). Social organizations participating in HECS seems to be a promising way to address these problems but also raises new challenges, like uncoordinated cooperation among stakeholders, which could lead to low management efficiency and low service quality. However, Synergetic development can be promising to enhance the participation of social organizations and to improve social welfare. This study introduces a conceptual model to explore relationships between five determinants and synergetic development of social organizations participating in HECS. A structural equation model (SEM) based on questionnaire survey is used as a test methodology. The results indicated that stakeholder engagement plays a critical role in synergetic development in HECS, resource allocation can only be improved by institutional climate, and supervision capacity cannot facilitate information sharing. This study provides effective strategies and directions for the improvement of home-based elderly care services.