College students with attention deficit hyperactivity disorder (ADHD) are a growing population, and they bring strengths and unique ways of processing information and solving problems. However, the academic success of students with ADHD has lagged behind that of their peers without ADHD, and higher education has not traditionally been designed to promote the academic success of students with ADHD. This study expands, then applies, an existing student success model that includes measures of students' pre-college and college experiences. We used structural equation modeling to fit the hypothesized model with multi-institutional, longitudinal data from more than 45,000 first-year college students including more than 2,000 students with ADHD. In this model, having a previous ADHD diagnosis is associated with slightly lower first-year grades than students without a previous ADHD diagnosis. Further, the relationship between ADHD and first-year grades is mediated (explained) by academic adjustment (i.e., time management, study skills, understanding of professors' expectations, and adjusting to college academic demands). The implications of this study for higher education include recommendations for institutional and instructional change.