The Green Spaces, Learning Places (GSLP) environmental education initiative runs schools-based and community-based sessions to create opportunities for children and young people to engage with green outdoor environments in London, England (including parks, heaths, and forests). Bespoke evaluation resources were developed by researchers in collaboration with the GSLP delivery teams. The evaluation was based on before and after survey responses from 504 school-aged children (5–10 years) and 54 young people (13–19 years), observation of 62 children, and interviews with 18 children and 8 young people. The mixed methods findings suggest the programs had a positive influence on increasing participants’ understanding, confidence, nature connection, wellbeing, and involvement in green outdoor environments.