This study was designed to verify that the sense of calling of social workers have effect on organizational citizenship behavior along with the mediating effects of organization trust. Research participants were social worker working in social work agency located in Busan city, data was collected through mailed self-administered questionnaires and among the collected 349 surveys, 323 answers were used in the final analysis. Research results showed that the sense of calling of social worker has a significant positive effect on organizational citizenship behavior and that it also has indirect effects through organizational trust. In other words, while the sense of calling of social worker directly increases organizational citizenship behavior, it also increases organizational citizenship behavior by heightening organizational trust. With control variables, only the variable of job position had a significant positive effect on organizational citizenship behavior and gender, age, academic background, marital status, and religion did not show any effects. Through the research results, practical proposals were made to systematically develop educational courses that can strengthen the sense of calling of social worker, prepare diverse actions so that social worker can trust in the organizations they belong to, and reinforce the organizational citizenship behavior of social worker.