Mushroom farms started to widely establish in Egypt to partially replace animal protein. The type Pleurotus ostreatus is common in small farms because low cost of production. Residues of mushroom cultivation contain highly nutritive compounds resulted from metabolic activity of the fungus. In this work, the extract of spent pleurotus mushroom was used as organic fertilizer to enhance rice growth and productivity. The chemical analysis of spent extract (SE) verified that it contain considerable amount of reducing sugars, phenolic compounds and other macro and micro elements. Tow laboratory experiments were designed to study the effect of SE on soil micro biota and cyanobacteria. A field experiment continued for two successive seasons 2018 and 2019 was conducted where rice grains were soaked in SE then SE was applied by three methods, spraying on rice shoot system, soil drench and combined spraying plus soil drench. Results indicated that, SE improved soil microbial activity represented by total bacterial, fungal count and dehydrogenase activity in addition to soil respiration. Results of field trial indicated that the effect of soaking treatment was significant in spike length, number of full and empty seeds, grain and straw yield and nitrogen percent in grains,while the most effective treatment was the combination between sprayieng and soil amendement where the yield of grains and straw were clearly enhanced in addition to other yield characters.