First-year seminars are frequently designed to help students adjust to and succeed in college. Although considerable literature has explored this topic, many previous studies may have notable problems with self-selection, since students who choose to participate are likely more motivated academically than those who do not. Therefore, this study used quasi-experimental analyses within a large, longitudinal, multi-institutional dataset to explore the link between seminar participation and several student success outcomes. Overall, the use of propensity score analyses substantially alters the results, such that first-year seminars are positively associated with first-year college satisfaction, but they have no effect on fourth-year satisfaction, college grades, retention, or four-year graduation within the full sample. This lack of impact is largely consistent regardless of whether the seminar is designed to engage students in academic inquiry or to promote orientation and academic success. Additional analyses observed some differential effects of first-year seminars by race/ethnicity, ACT score, and sex; the most consistent finding is that first-year seminars appear to promote the college grades and college satisfaction of Black students. Implications for future research and practice are discussed.