This work amid to investigate the beneficial effects of the biostimulating treatments under treated Sewage water. Foliar spraying of salicylic acid at 0.5 and 1 g^-1, chitosan 2 and 4 ml^-1 and alage extract at 2 and 4 ml^-1 start at June and repeated 8 times on growth, flowering and fruit quality of olive trees grown under treated sewage water applications. Results indicated that chitosan at 4 ml^-1 significantly increased growth parameters fresh weight of leaves/branch g, dry weight of leaves/branch and total leaf area/branch cm². Flowering characteristics i.e., date of full bloom, flowering density, total number of flower/inflorescence. In addition, fruit yield/tree, fruit yield /faddan (ton), fruit weight g, fruit width (cm), fruit length, seed weight, flesh weight, percentage flesh/fruit weight. Also, fruit chemical quality i.e., fruit moisture %, fruit oil content and refractive index, were increased with chitosan at 4 ml^-1 during both seasons. Meanwhile, peroxide value and acid value % were decreased with the same application during both seasons. Using chitosan is best superior for increasing olive growth and yield under treated sewage irrigation water.