Effect of three cucurbita varieties, cvs. ‘Ace’, ‘Shintozwa’ and ‘ShintoHongto’ as rootstocks, on survival rate and primary growth of melon cv. Khatooni as well as on muskmelon cv. Samsuri seedlings was investigated in greenhouse conditions. The rootstocks exhibited high compatibility (up to 97%) with scions with the response of muskmelon seedlings more pronounced than that of the melon ones. The root activity (synthesized formazan concentration per Dry Matter (DM)), in rootstocks was 2-3 times that in scions. All the rootstocks except ‘Shintozwa’ had more vascular bundles than scion plants. Such plant growth characteristics as root activity, stem length, rootstock stem diameter, leaf chlorophyll content and fresh weight of top organs were positively affected by grafting and by rootstocks (p = 0.01). Scion stem diameter, leaf number and leaf area were significantly affected by treatments at p = 0.05. Fresh weight of top organs and of root, as well as root dry weight were not significantly affected by grafting and by rootstocks. In most of the evaluated characters, grafted seedlings were in a more proper had better situation than non-grafted ones. Among the grafted seedlings, all the rootstocks experienced approximately similar effects. So, according to the obtained results, use of evaluated rootstocks for Iranian melon and muskmelon can be advisably recommended.