Despite the massive growth and benefits of online learning platforms, engaging and retaining learners showcases a major challenge in the present scenario. There is a dearth of literature on measuring the antecedent factors of learner engagement behavior through mediating effect in the online learning context. Therefore, the current study was designed to empirically confirm the factors influencing the learner's engagement in online learning platforms through the Unified Theory of Acceptance and Use of Technology (UTAUT) framework. The data was collected from 336 learners who have accessed online learning platforms. Structural equation modeling was tested to evaluate the proposed relationships in the conceptual framework. The results identified performance expectancy, facilitating conditions, learner self-efficacy, and e-learner's intention to use behavior as key antecedents of e-learner's engagement behavior in the online learning platform. Subsequently, the e-learner's intention to use behavior played a significant role as a mediator in influencing the e-learner's engagement. The novelty of the study is to offer statistical significance on limitedly studied phenomena in online learning towards investigating the e-learner's intention to use behavior as mediation in envisioning e-learner's engagement behavior. Additionally, the study theoretically contributes to the existing body of literature. Also, the study findings underscore the need for organizations, policymakers, and academic institutions to develop online learning platforms that enhance learners' engagement behavior.