This article adopts the concept of protagonismo infantil (children’s protagonism) to argue that children’s voices on gender identity need to be centred in order to fully empower trans and non-binary children. In this field of children’s rights, protagonismo infantil enables the law to act as a malleable frontier rather than as a rigid boundary. Topics concerning gender and sexuality do not feature prominently among the legal, social, and medical issues most widely discussed in terms of children’s rights. When they are approached, such topics are treated as marginal, controversial, and divisive. The dominant approach is to deny and disregard any possibility for children’s self-identification in terms of gender and/or sexual orientation, and to ‘wait and see’ until an older age – in some cases, adulthood. Yet every child is sexed and gendered at birth by medical and legal practitioners and parents, and gender and sexuality are core aspects of every individual’s sense of self and identity. Focusing mainly on the United Nations Convention on the Rights of the Child (UNCRC), this article encourages new debate on how children can be empowered to affirm their own gender identity through the use of protagonismo infantil.