THIS STUDY was conducted during two successive seasons 2013 …. and 2014 in private orchard at El-Behiera governorate (Latitude: 30.9833 Longitude: 30.2000), Egypt, to study the effect of spraying Moringa leaf extract, as a safe natural product compared to other substances on yield and fruit quality of 15-years-old Navel orange trees (Citrus sinensis) budded on Sour Orange (Citrus aurantium, L.Osbeck). Treatments used were; control (spraying with tap water), moringa leaf extract (MLE) at 3, gibberellic acid (GA3) at 30 ppm, chelated calcium (Ca) at 0.5%, and potassium nitrate (KNO3) at 1%. They were sprayed at full bloom stage, fruit set, at last week of June and at complete mature stage. The obtained results revealed that, treatments in general improved significantly Navel orange fruit set, where GA3 and MLE treatments gave the highest value. The highest yield was induced by MLE followed by other treatments. While, MLE treatment gave the lowest fruit peel firmness compared to other ones. In addition, MLE and GA3 treatments increased juice percentage and gave the highest TSS %. On the other hand, MLE treatment increase significantly juice acidity compared to the other treatments. Moreover, KNO3 treatment gave the highest values of nitrite and nitrate in fruit juice, while GA3 and MLE treatments were the lowest. KNO3 and MLE significantly increased leaf N and K contents. Whereas, treatments in this study had insignificant effect on leaf P% content in both seasons. Thus, overall, based on the current results, moringa leaves extract can be used at rates of 3% to stimulate the biomass production of Washington navel orange trees yield, enhance leaf mineral content and some physical and chemical characteristics.