The Fandogloo jungle is located in the Ardabil province of northwestern Iran, and contains the largest in situ germplasm collection of hazelnuts (Corylus avellana L. ) in Iran. In this study, 12 quantitative and 21 qualitative traits of 70 wild hazelnut genotypes native to Fandogloo were studied, including traits of nuts, kernel and tree morphology. Results showed that, hazelnut genotypes from Fandogloo were phenotypically diverse with significant variation found across most traits studied. Interestingly, they had a smaller nut and kernel size and weight, compared to some hazelnut germplasm pools previously studied around the world, overall they exhibited a higher kernel to shell ratio. Results also showed, there were strong CORRELATIONs between kernel length and kernel thickness (r=0. 878), nut length and nut thickness (r=0. 875), and kernel percentage and chlorophyll index (r=0. 617). Positive CORRELATIONs were also found between branching density and suckering (r=0. 487) and between the curvature of the nut basal scar and size of the pistil scar (r=0. 352). Principal component analysis of quantitative variables revealed that the first four principal components (PCs) accounted for 74. 2% of the total variation. Regarding qualitative variables, the first nine PCs accounted for 64. 3% of the total variation. Cluster analysis based on quantitative and qualitative traits resulted in a dendrogram with seven and eight main clusters, respectively. Some of the genotypes were not grouped according to their geographical distribution. Overall, this study revealed the presence of high phenotypic diversity in the hazelnut genotypes from Fandogloo region, supporting their breeding value for possible use in future.