The present study was carried out at Al-Amana nursery in Talkha district, Dakahlya Governorate, Egypt, during the summer season of 2014 to study the effects of different graft combinations between rootstocks and scion of watermelon (Citrullus lanatus (Thunb.) Matsum et Nakai) var. Lanatus cv. Aswan F₁. The experiment included thirteen treatments resulted from the combinations of four rootstocks [Jumbo F₁ and Nun 6001 F₁ hybrids [Cucurbita maxima (Duch.) ex. Lam.× Cucurbita moschata (Duch.) ex. Poir.], bottle gourd (Lagenaria siceraria Standl.) and pumpkin (Cucurbita moschata L.)] and three grafting methods [Hole insertion (HIG), Splice (SG) and Tongue approach (TAG)] as well as non-grafted plants as control. The obtained results illustrated that there was a high compatibility between Watermelon(scion) and Jumbo followed by bottle gourd then Nun 6001 rootstock, where these graft combinations recorded the highest vascular thickness and area of vascular cambium compared to other graft combinations. Although, SG gave the highest area of graft union. In addition, TAG showed the greatest width of graft union which is related to increase of xylem and phloem tissues thickness and area of vascular cambium. Moreover, grafted plants onto Jumbo and bottle gourd using TAG method recorded the highest survival percentage (100 and 98%, respectively) in comparison with other graft combinations. While, grafting onto pumpkin rootstock using HIG method had the lowest values of all studies traits in comparison with other combinations. Generally, the callus development and graft success in Watermeloncv. Aswan F₁can be performed using Jumbo rootstock with TAG followed by SG method.