For the past few decades, numerous theoretical perspectives have predicted a negative association between adolescent sexual debut and the probability of college entrance. The present article extends the literature by using nationally representative longitudinal data from South Korea to assess these perspectives. Drawing on longitudinal data from South Korea, this article examined the impact of becoming sexually active between 8th and 12th grades on the probability of college entrance. We controlled for a wide array of confounding variables by using logit models that account for longitudinal attrition and school-based sampling design. Analytical results showed that the initiation of sexual intercourse during adolescence predicted a statistically significant decrease in the probability of college entrance for both boys and girls. Gender-specific analyses suggested that, on average, sexual debut in adolescence was associated with a decrease of 10.3 percentage points in the probability of college entrance for boys and a decrease of 14.7 percentage points for girls. These findings strongly support the theoretical perspectives of age norm theory and sexual double standards in South Korea, where strictly conservative attitudes toward sexuality and sexual behaviors are dominant. Copyright © 2020 The Foundation for Professionals in Services for Adolescents. Published by Elsevier Ltd. All rights reserved.