The chapter provides crucial information on climate change and its association with phytopathogens and food security. Climate change directly or indirectly influences food safety and associated health risks. The climate has been changing rapidly globally, resulting in devastating consequences upon social and environmental determinants of health such as clean air, safe drinking water, food chains, and food safety for humans. Climate change has become an unprecedented challenge for the planet’s ecosystem, biodiversity, human health, and global economy. Climate change has also been the most pressing problem in the field of plant health, and ultimately animal and human health. Moreover, climate change is adversely affecting agricultural production systems around the world, posing negative impacts on food security. It affects international trade flows of agricultural products and changes the invasion potential, exposure, and prevalence of pests around the world. Numerous studies carried out on grain or fruit crops demonstrate that the pest risk posed by pathogens, (viruses, bacteria, parasites, etc.) weeds, as well as other undesirable biotic and abiotic factors, tend to increase in agricultural systems due to climate change. Habitats of several plants and animal species are being negatively influenced by climate change due to changes in water availability and quality. This may lead to several terrestrial, freshwater, and marine species, to cause changes in geographic ranges, seasonal activity, migration patterns, population size, and inter-species interactions. However, the impact on the yield of most agricultural crops is quite severe. Numerous studies indicate that climate change affects biological systems at various levels, from genes to ecosystems. The biologists noted that climate change in association with anthropogenic factors negatively affects 82% of the main ecological processes; from genetic diversity to the functioning of ecosystems. Phytopathogens under climate change not only affect the decline in agricultural yields but also deteriorate their quality, thereby threatening food security. The chapter presents a detailed review and situational analyses on the impacts of climate change, biological processes, and diversity threatening food security. The purpose of this chapter is to assess the potential impacts of climate change on plant pests and on plants, animals, and human health.