Multilingual pedagogies are underdeveloped, particularly in early childhood, although they show promise in diverse contexts. Researchers have made a call for their development and research. Programmes that further the development of multilingualism in daily interactions are rare and little is known about their efficiency. Further, scholars agree on the need to design professional development programmes to develop the practitioners’ competences to implement these pedagogies. Researchers highlight the role of professional learning communities and of programmes involving both educators and teachers. However, these fields have been little researched. The project MuLiPEC addresses the need for the development of multilingual pedagogies in early childhood education, necessary to develop the children’s multiple languages and to capitalize on language diversity in Luxembourg. The project analyses the language pedagogies as well as the ways in which professional development on multilingual pedagogies contributes to changing educational practices. We will offer a 15-month-long professional development programme following the model of professional learning communities, to both educators and teachers working with 3 to 6-olds in the non-formal (e.g. crèches, maisons relais pour enfants) and the formal (e.g. précoce, nursery) educational sectors. The emphasis lies on the implementation of multilingual activities using pictures, rhymes and stories in daily practice and on the collaborative reflection on multilingual pedagogies.In order to develop in-depth and contextualized understanding of the practices from an insider’s and an outsider’s perspective, we will focus on 8 participants selected for best practice and representing 2 different formal and 2 non-formal settings from different regions of the country. The data from this qualitative longitudinal study with quantitative elements comprise observations; videos of the practices recorded by the researchers and the practitioners; observations of a PhD student; interviews with practitioners; conversations with children, and a survey. Data will be collected at regular intervals and follow a pre- and post-test design. The analysis concentrates on changes in the practitioners’ beliefs and knowledge of the manners in which multilingualism develops, the ways in which perspectives on multilingualism grow, and the impact on children’s interactions and multilingual repertoire. Findings of this educational research should deepen our understanding of the characteristics of multilingual pedagogies and the ways in which they can be developed.