This research aimed to investigate how achievement emotions predict, mediate, and affect academic achievement in online learning. Online learning has been proliferating, but little is known about how emotion mediates cognition in the Community of Inquiry framework. Recent progress in cognitive neuroscience provided the theoretical foundation for researchers to investigate emotion's role in online learning, especially academic achievement. The researcher of this study adopted a quantitative non-experimental research design to investigate how achievement emotions mediated, predicted, and affected academic achievement in the Community of Inquiry framework. The Partial Least Square Structure Equation Modeling (PLS-SEM) method was adopted for statistical analysis. The participants were 110 undergraduate university students enrolled in an online course called Digital Identity in the Spring and Summer semesters of 2021 in a large public university. The researcher of this study discovered activity emotions singularly and significantly mediated teaching presence and cognitive presence to predict and affect academic achievement. This research was the first to pinpoint the criticality of activity emotions to academic achievement in online learning. Although four limitations existed in this research, the findings of this research extended the Control Value Theory of Achievement Emotions into the Community of Inquiry framework. A new learning theory called the Cogmotion Theory of Learning was proposed for the asynchronous online learning environment. Thus, this research and the Cogmotion Theory of Learning can enable future researchers to specify new design principles based on the criticality of activity emotions for learners to realize better achievement and higher performance. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]