In this study, we explored the relationship among mentoring functions (MFs), direct supervisor need for achievement (DSNFA), and employee organizational citizenship behavior (OCB) from the perspective of conservation of resources (COR) theory. A sample of 242 dyads was selected from new employees and direct supervisors employed in four- and five-star hotels in Taiwan. The results revealed that MFs and DSNFA were positively related to new-employee OCB. However, DSNFA negatively moderated the relationship between MFs and new-employee OCB. That is, low DSNFA positively moderated the relationship between MFs and OCB more than high DSNFA did. The results were explained using COR theory, which states that the development of positive personality traits is limited to in specific circumstances. Organizations in the hospitality industry that emphasize on OCB should examine their human resource activities to optimize performance.