Introduction <p>Physical inactivity in young children and schoolification within early childhood education are worrisome trends that curtail young children’s natural inclination to move, play, and explore. There is a need for high-quality evidence on effective, sustainable, and scalable interventions integrating the concepts of movement, play and exploration in early childhood education. Realization of such efforts depends on kindergarten contexts and requires highly competent staff. Through transdisciplinary intervention research, we seek to respond to these child development challenges by developing and testing a holistic move-play-explore early years pedagogy. The main aims of the MoveEarly study are to investigate the 1) effects of professional development for kindergarten staff on child movement, play and exploration and whole-child development and 2) how different kindergarten contexts influence implementation and institutionalization of the intervention.</p> Methods <p>The study use a two-arm (intervention, control) cluster randomized design with 7- and 18-months follow-ups and will be conducted in Norway 2024–2026. We aim to recruit 50 kindergartens and 500 children aged 4&#xa0;years to provide sufficient power to detect effect sizes between 0.25 and 0.40. The intervention is nested within two levels: the kindergarten and the child. The main intervention is an 18-month professional development/education module for kindergarten staff, aimed at supporting staff in developing their capacity to deliver an early years pedagogy integrating movement, play and exploration for all children. The outcome evaluation (4-year-olds) includes a range of child-level outcomes, including physical activity, physical fitness, movement competence, creativity, adiposity, socioemotional health, well-being, self-regulation, and early academic performance. The process evaluation (staff and all children) will describe implementation and adaptation processes using several types of quantitative and qualitative data.</p> Discussion <p>Professional development of staff targeting a whole-child early years pedagogy that integrates movement, play and exploration in the kindergarten setting may provide a feasible avenue to enhance child health, development and learning. MoveEarly is designed to test this hypothesis to provide evidence for an early solution to lifelong public health and developmental challenges.</p> Trial registration <p><a href="http://www.ClinicalTrials.gov">www.ClinicalTrials.gov</a> identifier NCT06488508 (05.07.2024).</p>