Extension services are playing a very important role in mainstream climate change adaptation at the sub-national level, particularly in local communities. Cambodia is one of the countries that has been suffering from the negative impacts of climate change and natural disasters. Currently, the capacity of extension officers was found limited in the coastal area of Cambodia. The project “Building Capacity of Extension Officers to Help Farmers Better Adapt to Climate Change in the Coastal Area of Cambodia” is dealing with: (i) improve the capacity of extension officers with new adaptation technology that appropriate in the target area, (ii) gap identification between extension officers and farmers in providing or accessing adaptation extension services in the coastal area of Cambodia, and (iii) mainstream appropriate climate change adaptation options to the household level. The approach using in this project comprises Training of Trainers (ToT), gap analysis, and farmers’ training. This project aligned with APN strategic plan, Sustainable Development Goals, and Cambodia Climate Change Strategic Plan in 2014-2023. Under the framework of this project, the capacity building of 120 extension officers and 120 farmers will be enhanced on appropriate climate change adaptation options, and the gap of accessing extension services in the coastal area of Cambodia was identified.