This study was carried out during the two summer seasons of 2011 and 2012 at Sakha Agricultural Research Station Farm, Kafr El-Sheikh Governorate, Egypt on summer squash (Cucurbita pepo L.) El-Askandarani cultivar to study the impact of plant spacing(30,40 and 60cm between plants), nitrogen fertilizer sources (organic and inorganic) and foliar spray with biostmulants(garlic or yeast extracts) and their interactions on vegetative parameters and leaf chemical constituents.Resultes indicated that, the highest values of vegetative growth characters i.e., plant length, number of leaves, fresh and dry weight, leaf area and chlorophyll contents in leaves as well as chemical constituents of leaves(N, P, K, Fe, Zn and Mn)were recorded when plants growing at 60 cm between plants. Squash plants sprayed with 2.5cm\l garlic extracts recorded better growth performance and higher values of chemical constituents of leaves than unsprayed plants. Also fertilized plants with 50%organic+50%inorganic recorded the highest significant values of most aforementioned parameters compared with control. The best results of both vegetative growth parameters and chemical constituents of leaves were recorded when plants growing at 60cm between them and fertilized by 50%organic as compost +50%inorganic as ammonium nitrate (100 kg/fed.) and sprayed with garlic or yeast extracts at 2.5cm/l in both seasons. Therefore, this treatment could be recommended for improving squash plants performance under similar condition of this study.