Background and purpose: In recent years, there has been a growth in international studies about the impact of different types of professional development programmes for teachers. However, few studies have directly addressed the role of higher research degrees, such as a doctorate, as a strategy for teachers' professional development, and even fewer have investigated the impact of these higher degrees on teachers' quality, students' outcomes and the wider school environment. The study presented in this article focuses on the experiences of Polish and Portuguese teachers involved in doctoral education by exploring their motivations and perceptions of potential impacts on their practice. Design and method: This paper reports on the findings of the study from a wider research project carried out in Poland and Portugal that explored teachers' motivations, perceptions and experiences related to doctoral studies and the impact on their personal and professional lives. This study focuses both on teachers' motivations for pursuing a doctoral degree and their perceptions of the impact of holding a degree on their practice. The data were collected through semistructured, in-depth interviews with 16 teachers who held a Ph.D. degree in education. The data were analysed thematically, using qualitative methods. Results: Results of this study indicate that personal motives and professional development were dominant factors in teachers' decisions to pursue a doctoral degree. All of the interviewed teachers reported that they thought that holding a Ph.D. degree had had a positive impact on them as professionals, on their students' learning outcomes and, to some extent, on their working environment. This impact was considered mainly in terms of individual changes, with no relation to a systematic policy of school improvement. Conclusions: The results of this study suggest that the doctorate has a strong influence on teachers in terms of changing their professional practice and, therefore, supports consideration of it as an effective form of professional learning for teachers. However, in order to capitalise fully on the knowledge and expertise generated by Ph.D.-holding teachers and their capabilities for school improvement, this study highlights how important it is for the school staff and school management to be more thoroughly engaged in this process.