Mycotoxins produced by filamentous fungi pose significant health risks to humans and animals. This study was carried out to evaluate groundnut (Arachis hypogea L.) samples from markets in Maiduguri, Nigeria for mycotoxin-producing fungi using a cost-effective, culture-based approach. Fungal species were isolated via direct plating and identified through morphological and microscopic analysis. Sample moisture content, a key factor in fungal growth, was measured and found to be below 10%. Seven fungal species, namely Aspergillus ustus, A. clavatus, A. fumigatus, A. niger, A. penicilloides, Ulocladium chartarum, and an unidentified white cotton-like isolate, were identified. All the isolates tested positive in the ammonium hydroxide vapor test, indicating mycotoxin production potential. Despite low moisture levels suggesting safe storage, the presence of mycotoxigenic fungi highlights a health risk if contaminated groundnuts are consumed. Given the high cost and complexity of conventional mycotoxin detection methods, this study advocates the ammonium vapor test as a rapid, affordable preliminary screening tool for identifying mycotoxin-producing fungi in food and feed, particularly in resource-constrained environments.