Two field experiments were carried out on clay soil in El-Gemmeiza Agric. Res. St., ARC, El-Gharbiya Governorate, Egypt during 2015 and 2016 seasons to study the effect of four phosphorus and boron fertilizers sources on leaves chemical composition, photosynthetic pigments and water relations, growth, seed cotton yield/fed and its components and fiber quality of Egyptian cotton cultivar Giza 86. A split-plot design with four replicates was used, where the main plots included treatments of phosphorus namely; A- Soil application of 22.5 kg P₂O₅/fed. as superphosphate (Control), B- Phosphate rock + Phosphorein (400g/30kg seed), C- Foliar application of 2 ml phosphoric acid/liter water, and D- Phosphorein (400g/30kg seed)., and the sub plots involved the sources of boron namely; 1- Control (without application), 2- Foliar spray with boric acid, 3- Foliar spray with B-Nano, and 4- Foliar spray with B-EDTA.  The obtained important could be summarized as follows: 1-The phosphorus sources gave significant effect on leaves N, P, K, photosynthetic pigments, total sugars, total carbohydrates and proline contents, leaves water content, water deficit, relative water content and osmotic pressure in 2016 season, No. of open bolls/plant, boll weight, seed cotton yield/plant, seed cotton yield/fed, lint percentage and seed index in both seasons, in favor of soil application with 22.5 kg P₂O₅/fed, final plant height and No. of sympodia/plant, in favor of foliar application with phosphoric acid.2- Foliar application with boron treatments fertilization significantly affected leaves N, P, K, photosynthetic pigments, total sugars, total carbohydrates and proline contents, leaves water content, water deficit, relative water content, osmotic pressure and transpiration rate in 2016 season, plant height at harvest, No. of sympodia/plant, No. of open bolls/plant, boll weight, seed cotton yield/plant, seed cotton yield/fed., lint percentage and seed index in both seasons,  where the superiority was found in favor of foliar spray with B-Nano 5 g/liter water. 3-The interaction between phosphorus and boron fertilizers sources gave a significant effect on leaves N, P, K, photosynthetic pigments, total sugars, total carbohydrates and proline contents, leaves water content, water deficit, relative water content and osmotic pressure in 2016 season, boll weight, lint % and seed index in 2015 season and No. of open bolls/plant, seed cotton yield/plant, seed cotton yield/fed., in 2015 and 2016 seasons, in favor of soil application with 22.5 kg P₂O₅/fed and foliar spraying with B-Nano 5 g/liter water.4- Upper half mean length, uniformity index, micronaire reading and fiber strength did not affect by the different phosphorus and boron sources and their interaction in both seasons.