Dutch sexual minority youth and young adults (106 females and 86 males, 16-24 years old) were assessed to establish whether there was a relation between gender nonconformity and psychological well-being and whether this relation was mediated by perceived experiences of stigmatization due to perceived or actual sexual orientation and moderated by biological sex. The participants were recruited via announcements on Dutch LGBTQ-oriented community websites and then linked to a protected online questionnaire. The questionnaire was used to measure gender nonconformity, perceived experiences of stigmatization, and psychological well-being. Gender nonconformity was found to predict lower levels of psychological well-being and the mediation analysis confirmed that lower levels of psychological well-being were related to the perceived experiences of stigmatization. This mediation was not moderated by biological sex. These findings show that both research and interventions should pay more attention to gender nonconformity among young people in order to create a more positive climate for young sexual minority members.