The purpose ofthis paper is to investigate seven uncertain factors (supply, demand, process, planning and control, competitors' action, climate condition and Thai government policy uncertainty) affecting on efficiency of Thai rice millers. The conceptual framework for this study is developed based on literatures in the environmental uncertainty of agri-food supply chain and its performance field. Efficiency is one important performance indicator in supply chain as well as agribusiness. Therefore, understanding certain uncertain factors influencing on efficiency of Thai rice millers is very crucial to manage them properly, and to obtain sustainable efficiency performance. The findings of this research show that particular aspects of demand and climate uncertainty are significantly related to decrease efficiency in the Thai rice millers.