Little is known about how gender contentedness is related to sex-related experiences among Taiwanese adolescents. Secondary analysis of data (n = 2624, Mage = 13.3 ± 0.47 years and 51% males) on a longitudinal youth cohort was used to track the evolving development of sex-related experiences such as exposure to sexually explicit media, romantic experiences, and sexual behaviors. Hierarchical multinomial logistic regression analyses were applied to study the effects of gender contentedness on sex-related outcome variables. The results showed that nearly 10% of the subjects were not contented with their gender. As compared to peers, gender-discontented adolescents had a higher likelihood of exposures to sexually explicit media (odds ratio [OR]. = 1.70, 95% confidence interval [CI]. = 1.18–2.46) and risky sex behaviors (OR = 2.22, 95% CI = 1.03–4.81). These results shed light on the impact of self-perceived gender contentedness on sex-related experiences in Taiwanese adolescents. Our findings are helpful for the development of practical guidance on sexual health issues, particularly for those who are discontented with their gender.