In this study, we develop and test three measures for conceptualizing the potential impact of co-enrollment in different courses on students’ changing risk for academic difficulty in a focal course. Two of these measures, concurrent enrollment in at least one difficult course and academic difficulty in the prior week in courses other than the focal course, significantly increase students’ odds of academic difficulty in the focal course in our models. Our results have implications for the designs of Early Warning Systems and suggest that academic planners consider the relationship between course coenrollment and students’ academic success.