This paper reports on a qualitative study which investigated a group of student teachers' emotions in their second language (L2) learning experiences, with particular attention to the mediating role of language ideologies. The findings revealed that the participants reported both positive emotions (enjoyment and pride) and negative emotions (anxiety, frustration and embarrassment) in their L2 learning experiences. In particular, these different emotions were found to be mediated by multiple and sometimes conflicting language ideologies, including the ideology of native-speakerism, the World Englishes ideology and the ideology of language as a tool for communication. The findings also showed that the different emotions evoked in the participants' L2 learning experiences not only impacted on their identities as L2 learners and L2 users/communicators in divergent ways, but also shaped their goals and agentive efforts in their subsequent L2 learning. Overall, the analysis points to the complex, dynamic and reciprocal relationship between emotions, language ideologies, identities and agency in understanding the affective dimension of L2 learning in a more holistic manner. It also calls attention to the potential of incorporating reflections on L2 learning experiences in student teachers' professional development programmes in order to enhance their emotional awareness for L2 learning and teaching.