Walnut is an important nut crop worldwide. Iran is one of the walnut centers of diversity and cultivation. Morphological traits and RAPD primers were applied to determine genetic diversity among 31 Iranian and four foreign walnut genotypes. From 14 RAPD primers, 180 bands were amplified among which 174 were polymorphic. The lowest and highest similarity coefficients were 0.37 and 0.89 respectively. Cluster analysis as based on Jaccard's similarity coefficient and UPGMA method divided the genotypes into five groups at similarity level of 0.50, the main groups of which consisted of 31 genotypes including the 4 foreign cultivars. Factor analysis resulted in estimation of three factors distributed among 67.4% of total variance. Factor analysis showed that most genotypes contained the main factor with ‘NFE3’, ‘NFE5’, ‘JAHAN1’and ‘CCGM1’ carrying the highest eigenvalue in the second factor, and each forming a separate cluster. In conclusion, RAPD markers were shown to be an efficient technique for studying genetic diversity in walnut. The genotypes with different genetic bases of suitable horticultural traits showed to be good candidates for walnut improvement programs.