This study was carried out at theExperimental Farm of Faculty of Agriculture (Saba-Basha), Alexandria University, Egypt ,at Abees region during 2013/2014 and 2014/2015 seasons to study the effect of phosphorus and potassium fertilizer rates and different biofertilization treatments on growth, yield, yield components and chemical grain contents of six rows barley (Hordeum vulgare, L.) variety Giza 123.The  experimental design used was a split- split plot with three replicates, where the three phosphorus application rates (0, 37.2 and 74.4 kg P₂O₅ /ha) were randomly distributed on main plot, three potassium fertilizer levels (0, 57.6 and 115.2 kg K₂O/ha) were located in sub-plots, whereas the three biofertilization treatments i.e. uninoculation, inoculation with phosphorein and inoculation with potassmage were occupied the sub-sub plots. Application of 74.4 kg P₂O₅ /ha significantly gave the highest value of yield and its attributes i.e. plant height (cm), number of tillers/m², spike length (cm), number of spikes/m², number of grains /spike, spike weight/m², 1000-grain weight (g), grains yield (t/ha), biological yield (t/ha) and harvest index (%) and N, P, K and protein percentages in grains. Increasing potassium application of 115.2 kg K₂O/ha increased the yield and its components, as well as, all chemical composition in grains. Inoculation potassmage gave the highest yield and its components, also N, P, K and protein in grains. Also, the obtained results indicated that the favorable effect of the highest levels of the studied factors, i.e., 74.4 kg P₂O₅ /ha, 115.2 kg K₂O/ha and inoculation with potassmage on barley plant growth, yield and its attributes and grain chemical contents in grains.