Peer mentoring programs are commonly used to facilitate the transition of new students into higher education settings. Peer mentors' experiences and emotions during mentoring are important but under-researched. We report exploratory work to address this gap in a two-phase study using a grounded theory approach. In Phase 1 mentors in an Australian university responded to online (n=35) or face-to-face (n=10) questions about their emotions during a peer mentor program. Emotions were found to be primarily positive, mentors varied in the extent to which they express emotions, and emotions relating to different time points were evident. In Phase 2, we examined temporal dimensions of emotions in more depth with peer mentors in a German university and added anticipated future emotions to existing categories. Connections between mentors' emotions and their own early experiences at university were explored, with another category of recalled prior emotions being added. Our findings are consistent with previous research regarding the positive and negative emotional aspects of being a peer mentor and further contribute to the understanding of the complexity of emotions in mentoring, specifically peer mentoring in higher education settings.