The aim of this thesis is to investigate mathematics in the context of Swedish extended education, namely, school-age educare. The research builds on investigating and identifying possible meanings of mathematics in school-age educare practice. Two overarching research questions support this work: How is mathematics formulated in school-age educare through enactment processes and what does this imply for students and staff? What characterises school-age educare mathematics in relation to the material-discursive practices that can be created intra-actively?The thesis deals with the ideas of mathematical activities, informal mathematics, and materialities in entanglement with bodily actions in playful and creative settings. The research questions are addressed in five articles which together address the phenomenon of mathematics in school-age educare from diverse angles—from a broad perspective that frames enactments of policy documents in practice, to a narrower perspective of mathematical activities in entanglements with bodily actions and material engagements. Data were produced from fieldwork at two educare centres, and involved observations, interviews, and written communications. Additional material consists of interviews with teachers and their work on registering mathematical activities in the practice.Theoretical stances shifted during the research process—from a human-centred perspective to a non-human-centred, non-hierarchical and flat ontology. Theoretical tools include: the three aspects of policy enactment theory (interpretative, material, and discursive), activities and values associated with enculturation, and agential realism from a posthumanist perspective. In a broad sense, the theoretical tools were used to analyse actions and expressions related to the phenomenon of mathematics in school-age educare. My findings relate to school-age educare mathematics in enactment orientations, in activities and values, and in bodily and material engagements. One finding is that there were four enactment orientations regarding mathematics being enacted in educare which highlight perspectives of mathematical positioning, use of materials, and interpretations of policy documents in practice. Another finding relates to the conceptualisation of mathematical activities and values of school-age educare as a way of complementing school mathematics. The concept of mathemat-ing is construed based on findings. Mathemat-ing is defined as a special case of mathematical events, embracing bodily actions, creations, engagements, and ethical sensibilities in entanglements with materials. Assessment is not included in the conceptualisation of mathemat-ing. My findings indicate that mathematics in school-age educare is created within the involvement in material-discursive practice. Together my findings suggest an approach to mathematics embracing children to “be within” mathemat-ing events and become mathematical.