Financed by SIDA, Green Forum runs a Green Youth Leadership Program in Latin America, where with facilitation from the Fundación Ambiental Vida Verde (FUNVIVE) it supports green parties and their youth wings through capacity strengthening, support for youth-implemented change projects and networking opportunities. The PIL team facilitated a reconstruction of the program's Theory of Change and conducted a theory-based evaluation to inform its further development. The evaluators collaborated with Dr. Paulius Yamin Slotkus who applied a behavioral science approach to our analysis of the program's outcomes. In a final workshop with program stakeholders, we focused on desired change in the behavior of the participants and determinants needed for the changes to take place.