This study was conducted at El-Baramoon Research Station, Dakahlia Governorate, Egypt during the growing seasons of 2015 and 2016 to study the effect of three water quantities (800.34, 1600.73 and 2400.40 m3/fed as common used treatment) and some antitranspirants, i.e., kaolin solutions 4%; as aluminum silicate, calcium carbonate (6%) as well as humic acid as potassium-humate (80% humic acid, 11-13% K2O) and their interactions on growth, yield, quality and some antioxidants of broccoli. The second level of water irrigation (1600.73 m3/fed) with application of kaolin or humic acid or the first level (2400.40 m3/fed) with application of kaolin or humic acid had the most significant effect of plant height, number of leaves/plant, dry weight/plant, leaves area/plant, central and lateral head weights/plot, total head yield/plot and total head yield/fed in both seasons of study, without significant differences between them. Increasing irrigation quantity from 800.34 to 2400.40 m3/fed increased broccoli growth characters in the both seasons. No significant differences were found in vegetative growth and yield attributes betwee water quantities of 1600.73 and 2400.40 m3/fed in both seasons. Kaolin or humic acid led to significant increase in most vegetative growth and yield traits compared to control. The third level of irrigation water quantity (800.34 m3/fed) with kaolin application had significant increases in antioxidants (vitamin C, anthocyanin, phenolic compounds and total flavonoids content). On the other hand, the application of high level of irrigation water quantity (2400.40 m3) and application of kaolin had a significant effect on protein content, in both seasons. The low level of irrigation water (800.34 m3) significantly increased the antioxidants content and decreased protein content in both seasons. Application of kaolin was significantly increased in all antioxidants and protein content in the both seasons in comparison with other treatments. Generally, it could be concluded that kaolin or humic acid application under water quantity of 1600.73 m3/fed was the best combination for broccoli production aimed at maximum water use efficiency in this study. This in turn encourages such amendments to reduce water consumption by 33.3%.