Turnover has been a serious concern to social service organizations. A lack of committed social workers is a risk to organizational performance and service quality. Therefore, it is vital to better understand the leaving process of social work practitioners. The study constructed a moderated mediation model to examine the mediating role of job satisfaction between employees' professionalism and turnover intention and the moderating role of the perceived level of managerialism in the context of social work organizations. A total of 667 participants from Guangzhou, Shenzhen, and Shanghai in China were recruited to complete the survey. Results presented that job satisfaction plays a full mediation role in the relationship between professionalism and turnover intention. In addition, the positive relationship between professionalism and job satisfaction, as well as the negative relationship between professionalism and turnover intention were moderated by managerialism. The findings enrich knowledge about turnover among social workers in the context of China and inspire to foster professionalism among service workers to improve job satisfaction and alleviate turnover intention and actual turnover as well as to apply management techniques and structures properly to strengthen the effect of professionalism on promoting job satisfaction and on preventing turnover intention.