The purpose of this study is to investigate the mediating role of proactive behaviors in the mechanism which job crafting affects organizational effectiveness. Through this study, we tried to contribute to the following theoretical and practical aspects. First, we tried to extend the theoretical discussion by identifying the relationship between job crafting, proactive behavior, and organizational effectiveness. Second, we provide practical implications for Korean organizational members based on proven job crafting, proactive behavior, and organizational effectiveness, and contribute to creating a work environment that enhances job satisfaction and reduces turnover intention. The results of this study are as follows. First, increasing structural job resource, increasing social job resource and increasing challenging job demand, which are sub-factors of job crafting, had a positive effect on job satisfaction. Second, increasing structural job resource, increasing social job resource and increasing challenging job demand, which are sub-factors of job crafting, had a negative effect on turnover intention. Third, job crafting had a positive effect on proactive behavior. Fourth, proactive behavior mediated the relationship of increasing structural job resource, increasing social job resource, increasing challenging job demand, and job satisfaction. Fifth, proactive behavior mediated the relationship of increasing structural job resource, increasing social job resource and turnover intention. This study provides an understanding of the impact of job crafting on organizational effectiveness and is expected to contribute to future research on job crafting.