Little is known about thallium behavior in the environment, especially its interactions with microorganisms such as fungi. This article evaluates basic interactions (bioaccumulation, biosorption and growth inhibition) between thallium and the common heat-resistant fungal species Neosartorya fischeri. The results suggest that the N. fischeri strain is relatively resistant to elevated concentrations of thallium in cultivation media up to 1 mg·l^-1. However, the toxic effect of thallium on fungal growth depends on the time of cultivation, and after 30-day cultivation growth inhibition was reduced. The bioaccumulation of thallium after 30-day cultivation by fungal strain was 35.74 mg·kg^-1 and 432.91 mg·kg^-1 for initial concentration 1.012 and 4.861 mg·l^-1 of Tl(I) in medium, respectively. The biosorption capacity was calculated to be 11.77 mg·kg and 62.01 mg·kg^-1 for initial concentration 1.012, and 4.861 mg·l^-1 of Tl(I) in medium, respectively.