Mycotoxins are toxic secondary metabolites produced by filamentous fungi that may contaminate food and pose a health risk, especially in developing countries, where there is a lack of food security and quality is subsumed by food insufficiency. Aflatoxins are the most toxic known mycotoxins and are a significant risk factor for liver and kidney cancer, teratogenicity, undernutrition, and micronutrient malabsorption in both humans and animals. The main aim of the study was to determine the extent of fungal and aflatoxin contamination in peanuts and peanut butter being sold in both the formal and informal markets in Bulawayo, Zimbabwe. Eighteen peanut samples and 11 peanut butter samples were purchased from retail shops and the informal market. Fungal contamination was determined using standard mycology culture methods, while aflatoxin contamination was determined using high-performance liquid chromatography-fluorescence detection. Four of the six peanut samples tested for fungal contamination were infected with Aspergillus flavus/parasiticus, ranging from 3 to 20% of the kernels examined, while 27% (3 of 11) of the peanut butter samples were infected with A. flavus/parasiticus. Ninety-one percent (10 of 11) of the peanut butter samples were contaminated with aflatoxins (mean, 75.66 ng/g, and range, 6.1 to 247 ng/g), and aflatoxin B1 was the most prevalent (mean, 51.0 ng/g, and range, 3.7 to 191 ng/g). Three of the 18 peanut samples were contaminated with aflatoxins (range, 6.6 to 622 ng/g). The commercial peanut butter samples had very high aflatoxin levels, and manufacturers should be sensitized to the detrimental effects of aflatoxins and measures to reduce contamination.