The purpose of this study was to find out what current challenges successful principals in Estonia and Finland identify in developing their schools. The strategies used in dealing with these challenges were also analyzed within the framework of “growth-mindset pedagogy” as an educational approach to school leadership. The principals were interviewed, and the resulting data were analyzed by means of both inductive and deductive content analysis. The similarities among and differences between principals from Estonia and Finland were compared and discussed in the context of high-achievement-oriented but culturally different educational systems. According to the results, the challenges are similar in both countries, relating to the principals’ professional development, as well as developments in the curriculum and the learning community. The Estonian principals identified more challenges related to developments in the learning community than their Finnish peers, although in both countries they tended to use strategies related to growth-mindset pedagogy in dealing with them. Preparation and development programs for principals should pay more attention to their mindset and their views on teaching and learning, which may have a strong impact on the whole school community.