A field trial and a laboratory experiment were conducted during 2011 and 2012 seasons at the Experimental Station Farm, Faculty of Agriculture, MansouraUniversity and Seed Technology Research Unit at Mansoura, Dakahlia Governorate, Seed Technology Research Department, Field Crops Research Institute, AgriculturalResearchCenter. The main objective of this research was to study the performance of some soybean cultivars as affected by seed treatments and their effect on seed yield and its attributes as well as quality characteristics. Field experiments were laid out in a split- plot design with four replications. The main plots were occupied with three soybean cultivars i.e. Giza 21, Giza 35 and Giza 111. The sub-plots were assigned to eight seed treatments as follows; 1) Without seed treatment. 2) Treated seed with ascorbic acid. 3) Treated seed with fungicide Vetavax. 4) Treated seed with yeast extract. 5). Treated seed with ascorbic acid beside fungicide Vetavax. 6) Treated seed with ascorbic acid beside yeast extract. 7) Treated seed with fungicide vetavax beside yeast extract. 8) Treated seed with ascorbic acid beside fungicide vetavax and yeast extract. Laboratory experiments were conducted in factorial completely randomized design with four replications. Results showed that Giza 21 cultivar surpassed other studied cultivars in all studied characters, followed by Giza 35 then Giza 111 in both seasons. Treated soybean seeds before planting with the combination treatment of Ascorbic + Vetavax + Yeast surpassed other studied seed treatments and resulted in the highest means of all studied characters in both seasons. This treatment followed by treating seeds with Ascorbic + Yeast treatment, then Ascorbic, Ascorbic + Vetavax, Vetavax + Yeast, Yeast and lastly Vetavax treatment in both seasons. On the contrary, the lowest means of all studied characters were produced from control treatment (without seed treatment) in both seasons. According to the obtained results from this study, it can be concluded that, treated seeds of soybean cultivar Giza 21 with the combination treatment of ascorbic acid beside fungicide Vetavax and yeast extract could be recommend to raise soybean productivity and seed quality under the environmental conditions of Dakahlia Governorate.