The current study was performed at the Research Farm of Faculty of Agriculture, New Valley University during 2017/2018 and 2018/2019 seasons in order to evaluate response of onion cv. Giza 6 to some organic fertilizers, i.e., cattle manure and poultry manure in addition to mineral fertilizers as control treatment. The results obtained showed that the vegetative growth characters and yield components of onion plants were significantly influenced by fertilizers kinds. Combination of poultry manure at 75% of recommended fertilizers and 25% of mineral fertilizers recorded the highest values for both vegetative growth characters and yield components, i.e., plant height, leaves number, plant fresh  and dry weight, crop growth rate, bulb fresh weight, bulb diameter, bulb dry matter, marketable yield and total yield in a comparison to mineral fertilizers (control) in both seasons. While, the content of chlorophyll a, b, total carotenoids, N, P and K in onion leaves and vitamin C, sulfur volatile oil and TSS in onion bulb were increased significantly by application of poultry manure at 25% of recommended fertilizers plus 75% of mineral fertilizers compared to mineral fertilizers (control) in both seasons. It can be concluded that application of poultry manure at 75% of recommended fertilizers plus 25% of mineral fertilizers increased growth , yield and improved bulb quality of onion plants cv. Giza 6 under the New Valley Governorate conditions.