Despite the growing popularity of dual-credit courses as a college readiness strategy, numerous reviews of the literature have noted a number of important limitations of the research on the effects of dual-credit on student postsecondary outcomes. This study addressed these gaps in the literature by estimating the impact of dual-credit courses on postsecondary access, first-to-second year persistence, and eventual college attainment, and overcame many of the methodological limitations of previous studies. The study utilized a statewide longitudinal data system (SLDS), allowing us to track an entire cohort of students through their transition into postsecondary statewide. Propensity score matching was used in order to reduce the self-selection bias associated with high achieving students being more likely to take dual-credit courses. We explored how the number of dual-credit courses students complete and the subject of the courses influences their impact. We also compared the effects of dual-credit to alternative advanced courses. Our results suggest that dual-credit is a promising strategy for increasing the likelihood of students accessing, persisting through, and completing a degree in postsecondary, and is possibly even more impactful than advanced coursework. However, significant variation in the benefit of dual-credit exists.