Despite the growing rates of obesity and diet-related non-communicable diseases, globally, public health attention has only relatively recently turned to the links between trade agreements and the nutritional risks associated with it. Specific trade agreements appear to have played an influential role in the volume and types of foods entering different countries, yet there is currently no systematic and objective monitoring of trade agreements for their impacts on food environments. Recently, INFORMAS was set up to monitor and benchmark food environments, government policies and private sector actions within countries and globally. One of its projects/modules focuses on trade policy and in particular the food-related aspects of trade agreements. This paper describes the INFORMAS trade protocol, an approach to collecting food-related information about four domains of trade: trade in goods; trade in services and foreign direct investment; domestic supports, and policy space. Specifically, the protocol is tested in Fiji. The development and testing of this protocol in Fiji represents the first effort to set out a framework and process for objectively monitoring trade agreements and their impacts on national food supply and the wider food environment. It has shown that entry into WTO trade agreements contributed to the nutrition transition in Fiji through the increased availability of imported foods with varying nutritional quality. We observed an increase in imports of both healthy and less healthy foods. The application of the monitoring protocol also highlights challenges for data collection associated with each trade domain that should be considered for future data collection and analysis in other low and middle income countries.