The purpose of this scoping review was to identify studies where young children’s engagement in early childhood education and care (ECEC) settings was measured and to investigate conceptualizations and operationalizations of child engagement. The literature search conducted in March 2021 included ERIC, PsychInfo, Scopus and Web of Science databases and it resulted in 5965 articles, of which 286 were included in this review. Eligibility criteria were measurements of child engagement in any formal ECEC setting before starting first grade. Data was extracted about engagement conceptualization, theoretical frameworks, study population, study design, and engagement measurement tools and methods. The results showed variations both in the definitions and in the measurement of child engagement. The most common method of measuring children’s engagement in ECEC was observations by an external observer, followed by teacher surveys. Measures of general child engagement in ECEC have a focus on behavioral aspects of engagement while measures that focus on academic activities are more likely to include additional cognitive and emotional aspects of engagement. Child self-reports were rarely used and only present in measures of academic engagement of young children. About one-third of the identified studies relied on unestablished measures of child engagement. Seventy-seven unique established measures of child engagement were identified.