The aim of this thesis was to find ways that I, as curriculum leader, could enhance the teaching and learning of mathematics for preschool children. The children involved attend the Irish Government funded Early Childhood Care and Education scheme at my Early Year’s Care and Education setting. Underpinning this study was the desire to act in congruence with my epistemological and ontological values. I had observed and reflected upon the provision of early year’s mathematics teaching and learning in the preschool classrooms in my setting, and had uncovered a problem area. I found there was very little mathematical play, and thus minimal mathematics teaching and learning occurring. This was disappointing, given my epistemological and ontological beliefs, which are firmly rooted in Froebelian values of mathematical concepts, collaborative play, and the joy of learning. I strongly believe that early mathematical confidence and ability is beneficial to later academic success for all children. Thus the concept for my study was generated – “How can I as curriculum leader enhance the teaching and learning of mathematics in the ECCE classrooms in my early year’s’ setting for children aged 3-5 year’s?” The approach used was Self-Study Action Research. This study allowed me to observe and reflect upon my own practice as the curriculum leader of teaching and learning of mathematics for young children. The study was carried out within 3 preschool classrooms with the participation of 47 children in total, alongside their parents; and with assistance and input of 8 Early Year’s Teachers. The interventions carried out included enhancing the mathematics learning environment across the 3 indoor classrooms and the communal outdoor play area; the training of the 8 teachers in the subject knowledge of mathematical play and learning for young children; and providing information and support for parents to include mathematics in their children’s everyday lives. I also carried out a survey within the wider community of Irish early year’s educators to discover knowledge levels and attitudes regarding mathematics in the early years. Findings suggest that in my setting the participating children benefitted from an enhanced and intentional emphasis on mathematical play in their preschool and home environments. The early year’s teachers felt they learned a more intentional, informed and effective way to teach mathematics through play, without becoming too academic. Findings from the study include a need for a richly resourced mathematical environment to be in place; more focused and intentional learning about mathematics subject knowledge for early year’s teaching students; the requirement for a knowledgeable and well qualified curriculum leader in all early year’s’ settings; and a mathematics curriculum to be written and followed in all early year’s settings. In summary, this study has enhanced the teaching and learning of mathematics in the 3 preschool classrooms in my setting. We have added to and enhanced our mathematics environments, indoors and outdoors. We have written a mathematics Curriculum Policy document for our centre. We are in the process of training all early year’s’ teachers in rich mathematical play environments and intentional teaching and learning of mathematics through play. These changes will benefit children of all ages who attend. I feel prepared to support my team to continue to enhance their mathematics teaching, and to review other curriculum areas which could benefit from the Self-Study Action Research approach. We have developed a bank of training and educational materials to support all parents whose children attend the setting. I also feel confident to share these findings with the wider early year’s teaching community, and to potentially move the teaching and learning of early year’s mathematics forward for the young children of Ireland.