Two field experiments were conducted at the Experimental Farm Faculty Agriculture Mansoura University, Egypt, during 2006/2007 and 2007/2008 seasons to study the effect of water stress (irrigation at 24, 28,32 and 36cb) and mineral as well as bio-fertilizers combinations i.e. 100% of the recommended dose of NPK, 75% of the recommended dose of NPK alone or plus Alga 600 or plus Algreen or plus Amino total or plus Soft guard as a foliar spraying on yield and its components of onion. Results showed that increasing watering tension from 24cb through 36cb gradually with great significant decreased the averages onion bulb weight (g), bulb diameter (cm), total bulbs yield (t/fad), bulbs marketable yield (t/fad), and significantly reduced the losses percentage after 2+4+6 months in both seasons. However, increasing watering tension from 24cb through 36cb significantly increased culls bulb yield (t/fad) by each increase in irrigation tension. Normal irrigation of water supply at 24cb markedly recorded the heighst losses percentage of bulbs dry weight in both seasons. Results indicated that application of 75% NPK+ Soft guard significantly increased average bulb weight (g/plant), bulbs diameter (cm), total bulbs yield (t/fad) and marketable bulbs yield (t/fad) compared with the rest fertilization treatments. However, culls bulbs yield was not significantly response to mineral and bio-fertilization in both seasons. No significant effect was recorded due to the interaction between irrigation tension treatments and mineral as well as bio-fertilization on bulb weight (g), bulb diameter (cm), total bulbs yield (t/fad), culls bulb yield (t/fad) and bulbs marketable yield (t/fad), while significant interaction was recorded on post harvest losses percent after 2+4+6 months in both seasons.