In the context of complex intergenerational challenges such as climate change and sustainable development, it is increasingly important for scientists and policy-makers to actively engage with and support the meaningful participation of youth in policy and decision-making. This research evaluates the effectiveness and impact of the Youth in Landscapes Initiative in supporting the active participation and leadership development of youth (aged 18–30 years old) participants at the 2014 Global Landscapes Forum (GLF), an international science-policy forum. This ‘youth program’ comprised a Youth Session, skills workshops and mentoring programs to empower youth through leadership and capacity building opportunities. Results show a high demand for youth participation: 34% of GLF conference delegates expressed interest to attend the Youth Session, over 22% of GLF session organisers requested youth to take on leadership roles, and the youth program itself received over 770 applications for the ‘facilitator’ and ‘pitcher’ leadership positions. The skills-based ‘masterclasses’ successfully built the confidence and knowledge of youth participants, as shown by post-evaluation survey responses. This translated into active and substantive youth participation throughout the forum. Senior professionals connected to the program praised it highly, seeing it as an opportunity for mutual, intergenerational learning. The Youth in Landscape Initiative is presented as a model and distilled into a framework to inform future youth engagement strategies in international conferences and associated science-policy processes.