The changing landscape of early childhood education related to accountability-driven assessments is creating the need to understand how these changes effect engagement. Children's engagement in school is one of the leading predictors of learning (Carini et al. in Research in Higher Education 47(1):1-32, 2006; Fredricks et al. in Review of Educational Research 74(1):59-109, 2004). However, there appears to be a range of ideas about the conceptualization and measurement of engagement. This review investigates the conceptualization and measurement of engagement in early childhood education and how measures align with conceptualizations. Findings reveal engagement is defined as solely behavioral in eight (38%) of the 21-articles reviewed, with most articles (67%) measuring engagement through observations. Additionally, most articles (95%) align their conceptualization and measurement of engagement. Opportunities for fine-tuning approaches to measuring engagement in early childhood are discussed.