Abstract This study was conducted at the experimental farm of Shandaweel Research Station, Agricultural Research Center (ARC), Sohag Governorate, during the two seasons of 2016/2017 and 2017/2018 to study the response of some onion varieties different fertilization treatments (without fertilization, 100% NPK, biofertilizer + humic acid, bio fertilizer + humic acid + nano-ZnO, 75% NPK + Biofertilizer + nano-ZnO, 50% NPK + biofertilizer + nano-ZnO, 75% NPK + humic acid + nano-ZnO, 50% NPK + humic acid + nano-ZnO, mineral NPK 75% + Biofertilizer + humic acid + nano-ZnO and mineral NPK 50% + Biofertilizer + humic acid + nano-ZnO). The highest means of bulb diameter were recorded for Shandaweel 1, while the lowest means were recorded for Giza 20, in both seasons. The highest means of bulb diameter were obtained under the treatment of 75% NPK + bio fert. + humic + nano-ZnO at 90 days in the second season and at 120 days in both seasons, while the treatment of 75% NPK + humic + nano-ZnO appeared the highest values of bulb diameter at 90 days in the first season. Shandaweel 1 variety attained the highest values of plant fresh weight and plant dry weight at 90 days in both seasons, while Giza 6 Mohassan recorded the lowest values at 90 days in the 2nd season. The treatments of 75% NPK+ bio fert. + humic + nano-ZnO appeared the highest values of plant fresh weight and plant dry weight at 90 days, while the treatment of 100% NPK appeared the highest values at 120 days, in both seasons. The highest values of average bulb weight, total yield/fed and exportable yield/fed, were obtained by planting of Giza 20 variety under 75% NPK + biofert. + humic + nano-ZnO, in both seasons. The highest values of local marketable yield/fed, were obtained by planting of Giza 20 variety under 75% NPK + humic + nano-ZnO, in both seasons. The highest means of TSS% were recorded under the treatment of no fertilization in both seasons, while the lowest means were obtained under the treatments of 75% NPK + humic + nano-ZnO, in the first season and under 50% NPK + humic + nano-ZnO in the second season.