Iran has suitable conditions for cultivating high-quality varieties of hazelnuts (Corylus avellana L.). Most of hazelnut orchards in Iran have been established by planting native genotypes. Aspergillus flavus Link. (AF) is a filamentous fungus affecting hazelnut kernels in orchards and during storage conditions. The most widely explored strategy for reducing aflatoxin contamination is the development of host resistance. The relative susceptibility of 12 native and exogenic hazelnut varieties including Soorii, Gerd-e-Eshkevarat, Gerd-e-Shouk, Navan 1, Fertil du Cortard, Pashmineh 89, Rasmi, Gerje, Ronde du pimount, Shastak, Negret, Gerdooii, to AF contamination was evaluated as in vitro by the kernel screening assay. Hazelnut kernels were surface sterilized and then inoculated with spore suspension (1×106 spores/ml) of AF by dipping method. Experiments were done in a completely randomized design with four replications. After five days of inoculation and incubation at 28 °C, the criteria of the AF growth (sporulation density, SD %) and sporulation rate (SR, spores/ml) on whole (intact) and wounded (cut) kernels of hazelnuts were measured. Results revealed statistical significant differences among hazelnut varieties for the SD% and SR parameters (ρ≤0.05). The Averages SD% and SR of A. flavus on intact and wounded kernels ranged from 16.50-75.14%, 48.25-100% and 14.6×105-16.7×106, 12.6×107-47.6×107, respectively. The highest and lowest SD% on whole and wounded kernels was related to hazelnut varieties Pashmeneh 89 and Gerde-Eshkevarat, respectively. The cultivated variety Gerde-Eshkevarat was recorded as an important potential source of resistance to AF. Manuscript profile