It has been a pronounced concern for social service organisations (SSOs) on how to foster a sense of co-ownership amongst their employees. A total of 937 valid questionnaires were collected amongst social worker participants aged twenty-one to twenty-nine years working in three different places of China, namely, Hong Kong, Shenzhen and Guangzhou. By confirming the hypotheses, the findings revealed that decent work and social support were positively associated with the collective psychological ownership (CPO) held by young adult social workers, and decent work enhanced CPO shared by them through an indirect mechanism of enhancing their social support at work. This is the first-ever study providing empirical evidence to support the association of decent work and social support with CPO amongst young adult employees in organisational context. The findings of this study can help inform the development of human resources management strategies for cultivating CPO, justify and expand the promotion of decent work in conjunction with the framework of psychology of working theory and interpersonal perspective, and inspire relevant research and practice with regard to the personal development of young adult social workers and the sustainable development of SSOs.