Student engagement in online learning environments is of particular importance to successful learning experiences due to the unique features of online learning environments (e.g., physical distance, sense of isolation from peers and instructors). Reliable and valid assessment of student engagement is vitally important for making evidence-based decisions for online learning environments. Addressing this need and the limitations of the existing measures, this study presents a tool to assess student engagement in online learning environments, the Online Engagement in Higher Education (OEHE), which has been validated through a series of confirmatory factor analyses, as well as additional validity analyses, and internal consistency reliability analysis. Using data from 235 undergraduate and graduate students, who took at least one online course during the time of data collection in Fall 2021, a hypothesized three-factor model of online student engagement based on Fredricks et al.’s (2004) engagement framework focusing on three core dimensions of behavioral, emotional, and cognitive engagement was adequately confirmed in the context of CFA. The OEHE was also shown to have reasonable evidence of convergent validity and criterion validity, and strong evidence of discriminant validity through Pearson correlations. The OEHE subscales and the final validated instrument with 20 items also were found to have adequate or very high internal consistency reliability. Implications for the OEHE instrument development and validation and recommendations for future studies are discussed to provide insights for online engagement researchers, practitioners, and other stakeholders in online education.