Mycotoxins are secondary metabolites of filamentous fungi that may contaminate food plants, including nuts, depending on abiotic and biotic factors. They are of major concern worldwide as they may cause acute or chronic intoxication, and even death, in humans and animals. This chapter reviews fungal infestation and mycotoxin contamination of nuts depending on the environmental conditions and production practices. It then describes the pre- and post-harvest strategies to prevent and limit mycotoxin contamination throughout the nut production chain. Finally, it discusses how knowledge and research results are applied to the field, and how to improve and extend their use and effectiveness. The focus is directed towards aflatoxin contamination in groundnuts, especially in the main African producing regions.