OBJECTIVES: Early gender-affirmative treatment (GAT) of adolescents may consist of puberty suppression, use of affirming hormones, and gender-affirmative surgeries. This treatment can potentially influence sexual development. In the current study, we describe sexual and romantic development during and after treatment. METHODS: The participants were 113 transgender adolescents treated with puberty suppression, affirmative hormones, and affirmative surgery who were assessed as young adults (38 transwomen and 75 transmen; mean age 20.79 years, SD 1.36) during and after their GAT. A questionnaire on sexual experiences, romantic experiences, and subjective sexual experiences was administered and compared to the experiences of a same-aged sample from a Dutch general population study (N = 4020). RESULTS: One year post surgery, young transgender adults reported a significant increase in experiences with all types of sexual activities: masturbation increased from 56.4% to 81.7%, petting while undressed increased from 57.1% to 78.7%, and sexual intercourse increased from 16.2% to 37.6% post surgery compared to presurgery. Young transmen and transwomen were almost equally experienced. In comparison with the general population, young transgender adults were less experienced with all types of sexual activities. CONCLUSIONS: Early GAT (including puberty suppression, affirmative hormones, and surgeries) may provide young transgender adults with the opportunity to increase their romantic and sexual experiences.