Outdoor play is a basic element of child’s holistic development. And because children spent most of their time in ECD Centres, educators should understand how to provide them with sufficient play opportunities. In Kenya, there are many studies documented on outdoor play, but these studies failed to explain the school related factors that influence children engagement in outdoor activities. Thus, this study sought to investigate personal and material factors that determines children outdoor play behaviours. The study findings may help the Ministry of Education, County Government and educators to make right decisions regarding outdoor play in ECD Centres. The study was pegged on Maria Montessori’s theory of play. The literature reviewed in this study included availability of play materials, time allocation for outdoor play, teacher involvement in children play, and nature of outdoor playgrounds. Descriptive survey design was employed to explore determinants of children’s engagement in outdoor play. As per this study, children’s engagement in outdoor play was the dependent variable while independent variables comprised of aspects such as availability of play materials, allocation of time for outdoor play, teachers’ involvement in children’s play and nature of outdoor playgrounds. The study targeted 240 ECD Centres in Kwale County. Stratified random sampling was used to generate two strata: public and private, while simple random sampling was adopted to obtain 35 ECD teachers. Head teachers were purposively selected from each sampled ECD Centres. Data were gathered using questionnaire and observation checklist. The questionnaire was administered to teachers (n=35) and head teachers (n=24) while the observation checklist was used to record researchers’ observation about the available play materials, nature of playground, teacher’s roles during outdoor play and time allocated for children’s play activities. Qualitative and quantitative data analysis procedures were employed. Data were presented using frequency distribution tables, pie-charts and graphs. Chi-square was used to test the correlation between dependent and independent variables at level of significant of 0.05(P