The purpose of the present study was to investigate how early childhood teachers working in Head Start programs made meaning of preschool-age children's physical activity play by exploring their personal childhood and professional experiences with physical activity play. The study was conducted to contribute research-based recommendations for promoting evidence-based practices in young children's physical activity play at inclusive preschools serving diverse children and families. Thirteen early childhood educators from Head Start centers serving children who are ability, culturally, linguistically, and socioeconomically diverse in the greater Washington D.C. area participated in the phenomenological investigation. Data was collected via an in-depth phenomenological interview and two questionnaires. Findings provide research-based evidence that teachers' beliefs about physical activity play influence their practices and may be an important factor impacting the implementation of evidence-based practices in young children's physical activity play at preschool. Teachers' beliefs about the following factors influenced their professional practices related to physical activity play: disability, parents'/caregivers' responsibilities, the teacher's role during outdoor recess, interactions with siblings and peers, administrative policies, practices, and expectations, SES, gender, and the changing culture of childhood. Findings inform the design and delivery of effective professional development initiatives, as well as evidence-based recommendations for professional organizations for evidence-based practices for promoting preschoolers' physical activity play. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]