In parallel with the global climate change, the climate of Sri Lanka is also changing. High intensity rainfall, extreme warming and cooling, flash floods, and droughts are more common during the past couple of decades. It is obvious that these sudden changes in the environment may greatly affect food production, creating a tremendous pressure to the food security. To cope with these changes and minimize their impact, farmers are practicing various adaptation strategies. Researchers and scientists are also looking for possible adaptation measures in the long-term perspective. Further, by nature, Sri Lanka is blessed with a diverse spectrum of climatic conditions, as well as a great variability in soil and topographical characteristics. All these variations favorably affected the availability of a wide diversity of food crops, which range from temperate to tropical fruits and vegetables, while maintaining the nation’s food security in a wider perspective. Further, the availability of a wide array of underutilized fruits and other food crops, which have not been paid public or research attention yet, has a huge potential to increase the nation’s food security. The ability to withstand harsh environmental conditions of these underutilized, naturally grown food crops has to be extracted in future food security programs. This chapter’s goal is to establish a relationship between the nation’s food security and the consequences of climate change on agriculture and to discuss various adaptation and mitigation measures practiced by farmers and the climatic, soil, and topographic potential to ensure the food security. Further, possibilities of utilizing underutilized food crops in this regard was also discussed. The chapter concludes with a case study based on the crop model of the Agricultural Production Systems Simulator (APSIM), which may adapt a number of crops as a response to the scenario of future climate change while maintaining food security in tandem with population increase.