["Journal of Intellectual Disability Research, EarlyView. ", "\nABSTRACT\n\nBackground\nChildren with Down syndrome (DS) often do not meet daily physical activity requirements, which affects their participation in daily activities and overall quality of life. Structured physical activity programmes could address these issues, but accessible, participation‐based activities are limited.\n\n\nMethod\nThe Building Opportunities for Optimal physical activity Skills Training in children with Down Syndrome (BOOST‐DS) programme was designed, developed and content validated in three phases. A conceptual framework was developed from the relevant literature, followed by the identification physical activity components through brainstorming and discussions. The final content validation phase involved expert consensus using a modified Delphi method.\n\n\nResults\nThe BOOST‐DS identified 62 active play items across six domains of physical activity. After three Delphi rounds, 53 items achieved expert agreement.\n\n\nConclusion\nThe content‐validated BOOST‐DS programme includes 53 play‐based activities across six physical activity domains to enhance participation outcomes in children with DS.\nTrial Registration: The study was registered in the Clinical Trial Registry of India: CTRI/2023/08/056291 on 5 August 2023\n\n"]