Whether mentoring functions would help the mentees develope positive attitudes and behavior toward their jobs and organizations deserve further studied. This study examined the mediating effect of job satisfaction on the relationship between mentoring functions and organizational citizenship behavior (OCB) based on the matched samples of protégés and their mentors in the financial industry. Results of 103 paired respondents showed that mentoring functions were positively related to OCB, and job satisfaction mediated the relationship between mentoring functions and OCB. This study suggested that business organizations establish formal mentorship to enhance junior employees' positive attitudes toward their jobs, and then to increase their organizational citizenship behavior.