This article examines how children and youth exercise political agency – and confront its limits – within global climate governance processes linked to the United Nations Framework Convention on Climate Change (UNFCCC). It draws on 20 in-depth, semi-structured interviews with climate advocates aged 11 to 29 who have attended (or attempted to attend) UNFCCC Conferences of the Parties (cop s). Using an intersectional, rights-based framework informed by postpaternalist theory, we analyse the motivations, barriers, enablers and perceived impacts of child and youth participation. Findings show that peer mentoring and organisational support foster transnational advocacy, while adult-centrism, tokenism and material constraints continue to limit meaningful influence – particularly for participants under 18. Despite these challenges, young advocates adopt creative strategies such as informal lobbying, collective protests and digital campaigns. In doing this they assert their human rights and demand stronger climate action, including on fossil fuel phase-out and finance. We reflect on reforms necessary to strengthen the democratic legitimacy of global climate governance through the rights of children and youth.