Background and objective: This study examined the relationships between the perceived severity of unwanted pregnancy and attitudes toward four contraceptive methods (condoms, oral contraceptive pills, the withdrawal method, and the rhythm method) according to gender and sexual experience among unmarried university students in Korea. Material and methods: A descriptive cross-sectional comparative study was conducted among 1,372 unmarried university students (men, n = 755; women, n = 617). This was a secondary analysis based on a prior online survey. Descriptive statistics, the Kruskal-Wallis test, pairwise comparisons using the Mann-Whitney U test with the Bonferroni correction, and logistic regression were used to analyze the data in this study. Results: Female students with sexual experience had the highest scores for the perceived severity of unwanted pregnancy. In each group defined according to gender and sexual experience, differences in attitudes toward contraceptive methods significantly influenced the perceived severity of unwanted pregnancy. Conclusion: Efforts should be made to increase the perceived severity of unwanted pregnancy among female students who have favorable attitudes toward the rhythm and withdrawal methods. Students with sexual experience who use the rhythm and withdrawal methods should be targeted for educational interventions aiming to strengthen the perceived severity of unwanted pregnancy.