Numerous foodstuffs such as cereals, maize, nuts, and dried fruits have been found to be commonly contaminated with fungi and mycotoxins. Animal products such as eggs, milk, and meat have also been reported to be positive for some mycotoxins. The level of contamination differs across the world as the production of mycotoxins is impacted by environmental factors such as temperature, pH, and humidity. Agricultural products can be contaminated with mycotoxin-producing fungi before or after harvest. Plants affected by droughts and severe weather conditions are more susceptible to pathogenic fungi. The most prevalent mycotoxins are produced by the fungi of Aspergillus, Penicillium, and Fusarium. The major isolated mycotoxins are aflatoxins, ochratoxin A, patulin, trichothecenes, fumonisins, deoxynivalenol, and zearalenone. The effects of mycotoxins on human and animal health can range from acute to severe symptoms. Mycotoxin-contaminated foods have economic consequences for both consumers and producers, as food security and food safety are also impacted. This chapter focuses on the occurrence of mycotoxins in food and feeds that eventually enter the food chain. The effects of mycotoxins on humans or livestock and the limitations of international standards are also discussed.