The purpose of this study is to test the factors that impact the effects that compulsory citizenship behaviour (CCB) has on work-family conflict based on the theory of Conservation of Resources. Data were collected from 505 employees in 13 high-tech enterprises in China. It revealed that (1) employees’ compulsory citizenship behaviour is positively related to levels of work-family conflict, (2) work stress mediates the relationship between CCB and work-family conflict, and (3) proactive personality moderates the effects of CCB on employees’ work stress and work-family conflict, with the relationship more positive when proactive personality is high. The study contributes to the CCB literature through its identification of work stress as an important psychological mediation mechanism that amplifies the mechanism through which CCB has an effect on employees. The results provide a deeper understanding of important boundary conditions (in this case proactive personality) that impact the CCB to employee’s work-family conflict relationship. The findings also enrich the proactive personality literature. Paradoxically, if organizations attempt to foster citizenship behaviors by selecting people with the sort of proactive personality that might assist citizenship, they end up exacerbating the impact on work stress and work-family conflict. Theoretical and practical implications, limitations and promising avenues for future study are discussed.