The red flour beetle, Tribolium castaneum, is a common pest of stored wheat flour that can spread mycotoxin-producing fungi. This study investigated whether the beetle acts as a vector for these fungi in stored wheat flour from the Al Jouf region. Microbial flora was isolated from different life stages of T. castaneum and from the wheat flour itself. Then a combination of morphological, molecular, and phylogenetic methods was used to identify the species. Furthermore, mycotoxins were quantified and species were tested for antagonism between the microbes from the insects and the flour. A total of 354 isolates were collected: 142 from the insects and 212 from the flour. The insect isolates were dominated by the fungus Trichoderma harzianum (51.41%), followed by two bacterial species, Burkholderia gladioli (38.73%) and Bacillus amyloliquefaciens (9.86%). Meanwhile, the flour isolates included seven different fungal species, with Aspergillus flavus having the highest relative abundance (31.60%). Both fungal and bacterial species showed species’ overlap in their phylogenetic trees. Aflatoxin B-2 (9.56 ppb) and aflatoxin G-2 (0.85 ppb) exhibited the highest and least concentrations in the wheat flour, while, no aflatoxin was detected in the insect. Interestingly, the two bacterial species inhibited the growth of all fungal species, except for T. harzianum. The bacteria also showed a synergistic relationship with each other. These results suggest that T. castaneum is unlikely to serve as a biological host for toxin-producing fungi. Instead, we suggested that the insect role may be limited to the mechanical transmission of the fungi via contamination of their external bodies, movement, and dispersal of contaminants.