Tomato (Solanum lycopersicum) is one of the most economically attractive and widely consumed vegetables globally. Their high water content, perishability, transport and poor storage system predisposes them to spoilage by a broad spectrum of mycoflora resulting in huge postharvest losses. This study investigates antimycotic potential of alum on postharvest deterioration of tomato. Composite samples of deteriorating tomatoes were subjected to standard mycological analysis from which total fungal colony counts obtained ranged from 1.64x106-5.70x109 CFU/g, and the following species were identified; Aspergillus niger, A. flavus, Fusarium sp, Penicillium sp, Rhizopus stolonifer, Geotrichum candidium and Saccharomyces cerevisiae. In vitro antimycotic activity of alum (1% (w/v) concentration) was determined on some of the isolates by agar well method (AWM) and diameter of inhibition zone (DIZ) measured using a metre rule. G. candidum had the highest DIZ (9.0mm (29.0%) followed by A. niger (8.0 mm (25.8%) and 7.0mm (⁓ 22.6%) for Fusarium and Penicillium species respectively. R. stolonifer showed no inhibition or zero. pH values increased from 4.35-4.52 whereas TTA values decreased from 0.13-0.07 within 2days of analysis. However, these results indicate that treatment of postharvest deteriorating tomatoes with alum prior to consumption would enhance food safety as some of these fungi are known to be spoilage, toxigenic or opportunistic pathogens. So, their presence raises concern on storability as well as public health risks associated with consumption of these fruits. Therefore, production of tomato requires an integrated and multidisciplinary research approach not only to reduce economic loss but also create consumers’ awareness on potential public health hazards of consuming relatively cheaper and pathogen contaminated deteriorating tomatoes.