This study examined the relationship between career mentoring and work engagement from the mentor perspective, by estimating work meaningfulness as a mediator. The research model used quantitative survey data from 309 employees who mentored their junior colleagues in the on-the-job training programmes of Japanese companies. The results demonstrated that career mentoring had an indirect effect on the work engagement of mentors by enhancing the psychological meaningfulness of their work. In addition, learning goal orientation positively influenced career mentoring; this may subsequently facilitate the work engagement by increasing the perception of the meaning of work. Learning-oriented individuals who act as mentors find psychological meaningfulness in their work, which in turn enhances their work engagement. By setting acceptable meaningful goals for mentoring programmes, practitioners can minimize the negative outcomes of mentoring. The results contribute to the existing literature by examining how mentoring experiences affect the behaviour of mentors.