Field experiment was conducted with grapevine grown in sandy soil under drip irrigation at El Sadat city, Menoufiya Governorate, Egypt for two consecutive seasons (2006 and 2007) to investigate the effect of different sources of phosphorous fertilizers on Thompson seedless grapevine yield, average cluster weight, berry juice measurements, (TSS, Acidity, TSS/acidity) and chemical composition of blades. Four sources of phosphorous were used, i.e. phosphoric acid (H₃PO₄), monoammonium phosphate (MAP), ammonium polyphosphate (APP) and urea phosphate (UP) with two rates, 20 and 40 kg P₂O₅fed.^-1 applied as once, twice and three times /week through irrigation water. Results revealed that phosphorous at 40 kg P₂O₅fed.^-1 increased significantly vine yield and improved fruit quality more than 20 kg P₂O₅fed.^-1under all treatments. As regards to sources of phosphorous, yield ,cluster weight ,berry juice measurements and chemical composition of blades ,UP and APP were better than H₃PO₄ and MAP under the two rates and the different patterns of applications  Also the results showed that application of phosphorous fertilizers at three times /week was the best.