This investigation was carried out during two successive seasons of 2008 and 2009 on 15- year old Thompson Seedless grapevines grown in clay soil at 1.8 x 2 m to study the effect of biofertilizers as alternative nitrogen source to mineral nitrogen fertilization in vineyards. Mineral nitrogen fertilization (MN) was added at 80, 60, 40, 20 and 0 units per feddan with adding different biofertilizers (BF) i.e., Azotobacter chroococum, Azospirillum brasilens, Biogen, Microben and Nitrobene at  0, 25, 50 and 100 g per vine, respectively. Biofertilizers application significantly improved the vegetative growth indices i.e., leaf area, shoot length, wood ripening and cane's carbohydrates content. Cluster weight and yield/ vine were improved with application of 60 unites MN per feddan + 25 g Microbien per vine. Fruit quality was improved in term of soluble solid content: titratable acidity ratio, whereas nitrate and nitrite contents in berries juice were significantly reduced through using biofertilizers.