While a substantial proportion of students delay entry into higher education, sociologists are only beginning to understand the consequences of this phenomenon for educational attainment. Previous studies have reported a negative relationship between delayed entry and degree completion, but they have not been able to explain it with a range of students' background characteristics. Results from the National Longitudinal Survey of Youth of 1997 indicate that life course transitions, including work, marriage/cohabitation and parenthood, make a unique contribution to explaining this relationship. Adding life course transitions to the models that already control for a range of background characteristics helps to explain the negative relationship between delayed entry and degree completion. These findings have implications for studying educational success in higher education and understanding the process of educational attainment more broadly.