Student engagement is a multidimensional construct, indicates actual learning experiences and is affected by emotions. Negative and positive achievement emotions play an important role in engagement. In the light of Control-Value Theory and the Extended Process Model of Emotion Regulation, a model was developed and tested to investigate the relationship between student engagement and the antecedents of emotions. Participants consisted of 1450 pre-service teachers who were enrolled in degree programs at Faculties of Education in Turkey. The structural equation modeling method was used to test two research models developed for positive and negative achievement emotions. In the negative achievement emotions model, student engagement was influenced by control of learning beliefs, task value, negative achievement emotions, and reappraisal strategy, and these variables together explained 83.1% of the total variance in engagement. In the positive achievement emotions model, results revealed the effect of control of learning beliefs, task value, positive achievement emotions, and reappraisal strategy on student engagement, and these variables together explained 97.3% of the total variance in engagement. The findings have implications for expanding the theoretical knowledge about emotions and emotion regulation strategies to improve student engagement in online learning environments. This study suggests that it is important to pay attention to task value and emotions when designing online instruction and online learning materials and courses.