Background Workplace bullying depletes psychological resources, reducing job performance and organizational citizenship behavior. According to conservation of resources theory, psychological capital functions as a as a crucial psychological resource to influence the organizational citizenship behavior of employees who experience workplace bullying. Objective This study aimed to construct and validate a model of the associations between workplace bullying, psychological capital, and organizational citizenship behavior. Methods Meta-analysis and structural equation modeling (MASEM) was employed to analyze 40 quantitative empirical studies. Results Psychological capital was significantly and positively correlated with organizational citizenship behavior and significantly and negatively correlated with workplace bullying. However, organizational citizenship behavior was significantly and negatively correlated with workplace bullying, indicating heterogeneity among the variables. The total effects were as follows: workplace bullying negatively influenced psychological capital, psychological capital positively influenced organizational citizenship behavior, and workplace bullying negatively influenced organizational citizenship behavior. Psychological capital mediated the association between workplace bullying and organizational citizenship behavior. Conclusions Enterprises must address workplace bullying by establishing regulations and complaint channels. Additionally, they should prioritize recruiting employees with high psychological capital and develop employees’ psychological capital to enhance workplace contributions and organizational citizenship behavior.