Background The first few years of life have been identified as a critical stage in the development of activity behaviours, which have been shown to track into later life. This scoping review aims to assess the literature reporting on physical activity levels in the first 2 years of life in order to answer two main questions: (i) how is physical activity measured in this age group? and (ii) how active are infants and toddlers in the first 2 years of life? Methods A search strategy was employed using PubMed with restrictions only on age and language. After applying exclusion criteria, 20 papers were included in the results. Results Seventeen studies used some form of objective assessment of physical activity (accelerometers, actometers, direct observation, doubly labelled water or a metabolic chamber); while the remaining three relied on subjective assessments (parent reported questionnaires or interviews, and activity diaries). Nine studies exclusively assessed infants (<12 months), and five exclusively assessed toddlers (>12 months). Only six studies reported physical activity levels and patterns specifically; most included studies measured activity as a covariate or correlate. Therefore, much of the reported data was difficult to assess, as results were vague or incompletely described. Where data were reported sufficiently for analysis, results were equally conflicted regarding whether toddlers were meeting recommended physical activity guidelines. Conclusions This scoping review re‐iterates the fact that more studies need to be conducted, which focus primarily on measuring and reporting physical activity levels and patterns in this age group in a comprehensive and standardized way, so that more informed guidelines can be devised and interventions can be designed and implemented where necessary.