Children's everyday mathematics has been well evidenced by a growing body of research and is widely acknowledged as fundamental to meaningful learning in early childhood education. However, literature supports that drawing upon children's mathematical resources for further learning requires that the range of these resources is valued and noticed at school. Considering that up to now little is known about the way children express their mathematical ideas during naturally occurring activities within classrooms, this study sought to enhance our understanding of this issue. Informed by previous research on the emergence of early mathematics during play and based on the funds of knowledge framework, we investigated the content, the processes and the origin of children's mathematical knowledge in a kindergarten classroom, with the aim to understand through a sociocultural lens where and how this knowledge is situated and how this information is revealed during play activities. Evidence foregrounds the importance of examining all the different facets of children's everyday mathematics for creating responsive curricula and confirms the critical role of play for investigating this type of cultural knowledge within schools.