This study was carried out during two summer seasons of 2012 and 2013 at Sakha Horticultural Research Station Farm, Kafr El-Sheikh Governorate, on summer squash (Cucurbita pepo L.) Eskandarani cultivar to study the impact of phosphorus fertilizer levels 20, 40, 60 and 80 kg P₂O₅ /fed. and fruit thinning treatments;i.e.,  without thinning (control) , thinning the first fruit, thinning all fruits except the first and second ones and thinning the first and second fruit and their interaction on vegetative parameters and leaf chlorophyll contents. Results indicated that, the highest values of vegetative characters; i.e., stem length, plant fresh and dry weight, leaf area/plant  and chlorophyll content in leaves in both seasons  were recorded when plants fertilized with 80 kg P₂O₅ /fed. Number of leaves/plant  not affected by phosphorus fertilizer levels, in both seasons. Thinning the first and second fruit  produced the highest values of stem length, plant fresh and dry weight , number of leaves/plant, leaf area/plant  and chlorophyll content in leaves in both seasons. On the other hand, squash plants fertilized with 80 kg P₂O₅ /fed. with thinning the first and second fruit produced the highest values of stem length, plant fresh and dry weight , number of leaves/plant, leaf area/plant and chlorophyll content in leaves, while, squash plants fertilized by 20 kg P₂O₅ /fed. with thinning all fruits except the first and second ones produced the lowest value of each character. According to the mentioned results, the best results of both vegetative growth parameters and chlorophyll contents in leaves were recorded when squash plants fertilized by 80 kg P₂O₅ /fed. with thinning the first and second fruit ,therefore, this treatment could be recommended for improving squash plants performance under similar condition of this study.