The aim of this meta-synthesis is to deepen the understanding and knowledge of qualitative research focusing on education for mentors of newly qualified teachers. Altogether, 10 studies were included and synthesised. Four common themes emerged in the initial analysis: School and mentoring context, Theory and practice, Reflection and critical thinking and Relationships. Furthermore, three overarching dimensions were found as a final synthesis guiding the further development of mentor education: 1) Contextual dimensions, 2) Theoretical-analytical dimensions, and 3) Relational dimensions. The synthesis stresses the importance of a systematic, long-term and research-informed mentor education that develops mentors' (self-)understanding of teaching and mentoring.