This report presents a comprehensive regional mapping of Early Childhood Care, Nutrition, and Education (ECCNE) in Southeast Asia, led by SEAMEO RECFON. Launched in 2017, the ECCNE programme integrates essential components—enabling environments, parenting, care and education, health and nutrition, policy, and multi-sectoral participation—to support optimal child growth and development. To scale its impact regionally, SEAMEO RECFON conducted a mapping activity in 2021 using secondary data and internet research, complemented by macroeconomic and demographic data. Recognising gaps in available information, the Centre organized the Southeast Asian Learning Exchange Forum on Early Childhood Development Promotion in 2022, enhancing the data through expert consultations and country presentations. This report synthesizes findings into two parts: (1) an overview of HI-ECD implementation across Southeast Asian nations and (2) thematic and country-specific analyses that highlight national contexts, challenges, good practices, and policy recommendations. The report contributes valuable insights into the region’s progress and shared challenges in promoting holistic and integrative early childhood development.