Agaricus brasiliensis is popular because of its nutritional and medicinal properties. Brazil supplies this edible mushroom to international markets, where quality standards are very restrictive regarding the allowable concentrations of heavy metals, especially cadmium. In order to evaluate the accumulation of cadmium, chromium, and lead in A. brasiliensis, the fungus was grown as producers cultivate it, using plastic bags containing inoculated compost with soil as a covering. We analyzed the soil and compost using atomic absorption spectrophotometry to determine their physical and chemical properties and natural concentrations of the heavy metals cadmium, chromium, and lead. In addition to the metals naturally found in the soil and compost, 6.6 mgkg-1 cadmium chloride, 13.2 mgkg-1 chromium sulfate, and 1.2 mgkg-1 lead nitrate were added to the soil covering to simulate contaminated soils and to allow us to evaluate potential adsorption by the fungus. An analysis of the fruiting bodies after fructification showed accumulation of the heavy metals, with the greatest amount in those fruiting bodies that had been contaminated with cadmium. Furthermore, the contaminated fruiting bodies had the least raw protein content, were physically deformed, and exhibited variations in the results of Fourier transform infrared spectroscopy analyses.