Award-winning Green Preschools in Bali, Berkeley and Hong Kong were selected to explore the characteristics of Green Schools using measures developed by educators (Environmental Rating Scale for Sustainable Development in Early Childhood (ERS-SDEC)) and architects (simplified Leadership in Energy and Environmental Design (LEED) development). Classrooms for 4- to 5-year-olds were systematically assessed over a 10-month period. A 35 years' timeline of the Green School movement was produced. The Bronfenbrenner Ecological Theory has been used to frame and analyse this cross-national study. Results indicated striking similarities from both scales that the Green Preschool in Bali received the highest rating followed by Green Preschool in Berkeley and Hong Kong. Three distinct Green School characteristics were found to be: (a) holistic, (b) building and (c) curriculum. The schools' green characteristics appeared to be influenced by cultures, city regulations and the external institutions that established the green awards.