Cucumber seeds has been imported to Iran from different countries for many years. This has been done with limited works for native cucumber seed production. The first breeding step to performe mating design is the selection of appropriate parents for developing suitable cucumber hybrids. The North Carolina designs are used to estimate the genetic variation, genetic variance components and additive and non-additive variances. The aim of this study was to estimate the genetic parameters and heritability obtaied via a North Carolina Design I in a greenhouse of Agriculture department at Islamic Azad University of Isfahan (khorasgan) in 2015-2016. The 46 cucumber hybrids (from 10 cucumber genotypes as males with 27 breeding lines as females) were examined and tested in two separate designs. Crosses were done in according to a North Carolina I and then progenies were planted in a randomized complete block design with three replications in three sets in two separate experiments. The results of variance analysis showed that the effect of genotypes for all traits was significant in both two experiments. Also, the results of mean comparison of males for morphological traits in the first experiment revealed that the highest rate of morphological traits were from male crosses of 13, 2, and 21. The results of the second experiment for morphological traits showed that offspring of male lines of 1, 13, 14, 20 was higher than the other male lines. The highest broad sense heritability in the first experiment belonged to leaf length and the highest narrow sense heritability was for leaf width. In the second experiment, the greatest broad and narrow sense heritabilities were for shoot diameter. The highest and the lowest additive variance in the traits associated with yield in the first experiment respectively were observed in fruit weight and the average number of fruits. Also, in the first experiment, the highest and the lowest dominance variance were observed for fruit weight and the number of fruits. Totally, among the male lines, the progenies of male crosses of 13,7,14, and1 had the highest values of traits related to fruit and yield. Key words : heritability, cucumbers, additive variance, dominance variance