The present study was carried out at a private farm located in Bohout Village, Nabaroh District, Dakahlia Governorate, Egypt to assess the influence of different amounts of applied irrigation water, different types of antitranspirants and their interactions on vegetative growth parameters ( i.e, plant fresh and dry weights, plant length, number of leaves and Leaf area), leaf chemical constitutes ( i.e, N, P, K   percentage as well as total Chlorophyll (a+b) content and leaves   proline content)  and seed yield and quality ( i.e, seed yield plant^-1, plot^-1, feddan^-1,weight of 100 seeds and seed germination percentage) of squash plants (Cucurbita pepo L.) during the two successive summer seasons of 2012 and 2013 under drip irrigation system. The experiment included fifteen treatments resulted from the combination of three irrigation water levels (100%, 80%, 60% from ETc) and five antitranspirants (kaolin, CaCO₃, MgCO₃, green miracle and  tap water (control)). The obtained results showed that irrigation with 100% from ETc was the best irrigation treatment and the negative impact of drought appeared on studied characteristics with decreasing water supply to become more serious under irrigation with 60% from ETc. The frequent foliar application of antitranspirants played a remarkable role in alleviating the hazard of drought stress. However, all antitranspirants had promotive effects, kaolin foliar application gave the best results on all studied characteristics. It improved vegetative growth, leaf chemical constitutes and increased seed yield and quality parameters under both non-stress and stress conditions.  Moreover, Kaolin treated plants irrigated with 80% from ETc performed better even than untreated plants irrigated with 100% from ETc. According to findings of the current study, summer squash can be protected from the negative consequence of the drought by frequent foliar applications of reflective antitranspirants such as kaolin, as it proved to recover the growth as well as seed yield quality under water limitation conditions.