IntroductionPhysical activity in the early years is necessary for setting the foundation for healthy growth and development in later childhood and adolescence. While most published evidence to date focuses on typically developing children, prevalence rates of physical activity among children with disabilities have been less studied. This protocol paper documents the plan of a systematic review, which aims to synthesise the evidence regarding physical activity levels among young children with disabilities.Methods and analysisSearches are anticipated to commence in May 2022. Empirical quantitative studies will be considered for inclusion if they present intervention or observational data on non-therapeutic (ie, leisure time) physical activity among children <5.99 years with physical, mental, intellectual or sensory impairments. Data sources will be retrieved via electronic database searches (Cumulative Index to Nursing and Allied Health Literature (CINAHL), EBSCO Sports Medicine Database (SPORTDiscus), Medical Literature Analysis and Retrieval System Online (MEDLINE), Elsevier Bibliographic Database (Scopus), Psychological Abstracts (PsycINFO), Education Resources Information Centre (ERIC) and Excerpta Medica Database (EMBASE)). Additional strategies to identify relevant studies will include manual searching and citation tracking of included articles. Titles and abstracts of identified studies will be screened for inclusion, followed by full-text reviews. Three independent reviewers will conduct quality appraisal using the Downs and Black checklist. A summary of included studies will describe the study designs, participant and activity characteristics, and outcomes.Ethics and disseminationThis systematic review involves a secondary analysis of previously published data; therefore, this review does not require ethical approval. The proposed paper will summarise the current evidence base on physical activity levels among young children with a diagnosed disability. The findings from this systematic review will identify gaps to be explored by future research studies and inform future investigations among the paediatric disability population.PROSPERO registration numberCRD42021266585.