This article presents the findings of an analysis of the effects of CPD initiatives on the quality of the pedagogical practices of ECEC practitioners. It is part of a larger study commissioned by Eurofound and jointly conducted by VBJK, IOE and PPMI (Eurofound, 2015). In order to draw policy-relevant information that might support decision makers in designing effective ECEC policies in their countries, the study reviewed existing research evidence published on this topic not only in English, but also in all the languages currently in use in EU Member States. Therefore, it involved country experts from EU-28 Member States. The research question was framed by the political priorities identified by the Council Conclusions on Early Childhood Education and Care (EU Council, 2011). The systematic literature review methodology elaborated by the EPPI-Centre for informing evidence-based policies in the field of education and social sciences was adopted to review the evidence drawn from primary research studies cross-nationally. The study revealed that long-term CPD interventions integrated into practice, such as pedagogical guidance and coaching in reflection groups, proved to be effective not only in countries with a well-established system of ECEC provision and a high level of qualification requirements for the practitioners, but also in countries with poorly subsidised ECEC systems and low qualification requirements. CPD initiatives based on the active engagement of practitioners and on peer exchanges within a shared scientific framework, proved to be the most effective. (author abstract)