This investigation was carried out during the two successive seasons of (2007 and 2008) to examine the effectiveness of pre-harvest spraying of vitamin C (ascorbic acid) at 6 % and 12 %, yeast at 1 g/liter and 3 g/liter, sugars at 0.20 % and 0.30 % and gibberellic acid at 100 ppm and 200 ppm as well as control treatment on yield and fruit quality of Washington Navel orange fruits.          The obtained data indicated that fruit weight, yield (number of fruits per tree and weight of fruits per tree kgm) significantly increased with increasing the concentrations of all treatments. In addition, the highest values of fruit quality resembled by increasing total soluble solids, ascorbic acid, reducing sugars, non-reducing sugars, total sugars and decreasing fruit acidity.