Commercial feedstuffs are a basic element in modern pet husbandry in the world. In dogs, the effect of mycotoxins is severe and can lead to death. Few reports on the influence of dietary mycotoxins were found in the scientific literature. The aims of this work were to isolate and identify the mycoflora and to determine the aflatoxins (AFs) natural occurrence in raw materials and ready dry pet food. Therefore, the aflatoxigenic capacity of Aspergillus flavus species was investigated. Aspergillus was the prevalent genera (65-89%) followed by Penicillium and Fusarium spp. Aspergillus flavus was the most prevalent species, followed by Aspergillus sydowii, Aspergillus fumigatus and Aspergillus versicolor. Aspergillus flavus frequencies ranged from 58% to 86% except in sorghum meal. All samples assayed (except corn grains and ready pet food) showed Fusarium spp. contamination. Corn meal and corn meal and gluten samples had 100% Fusarium verticillioides. Fusarium graminearum was isolated from sorghum meal. Aspergillus flavus strains (75%) isolated from raw materials and 57% from pet food were able to produce AFs. All samples showed AFs contamination percentages over 70%; corn and sorghum meal obtained the highest AFs levels. Ready pet food did not show quantitative levels of the tested toxins. This is the first report of the aflatoxigenic capacity by A. flavus from Brazilian pet food.