Academic procrastination refers to individuals' unnecessary postponement of their coursework and is harmful for academic performance. When situated in self-placed and remote learning environments, students' tendency to procrastinate increases. Therefore, understanding why students procrastinate and identifying who is more likely to delay unnecessarily in online learning environments is an important area to study. The goal of this study was to respond to this call by examining the structural relations between conscientiousness, prior online learning experience, achievement emotions and academic procrastination in online learning environments using structural equation modelling. In particular, two main facets of conscientiousness--proactive and inhibitive--were examined in order to understand which facet was more responsible for procrastination, how each facet was related to procrastination and to determine which facet of conscientiousness should be the primary target for intervention in future experimental research. A total of 746 students from 49 secondary and postsecondary schools participated in the current study. The results showed that the proactive aspect of conscientiousness was negatively related to academic procrastination through the pathway of enjoyment. The inhibitive aspect of conscientiousness was negatively related to academic procrastination through the pathways of negative emotions. Although prior online learning experience did not have a significant and direct association with academic procrastination, it was indirectly related to students' tendency to put off coursework through the pathways of enjoyment and negative emotions. Of all the paths, negative emotions had the strongest associations with academic procrastination in online learning environments. The findings of indirect effects suggest that students with low conscientiousness, the inhibitive aspect in particular, and few prior online learning experiences are more likely to procrastinate in online classes possibly owing to the suboptimal emotional experiences aroused during their learning processes.