Two field experiments were conducted at the Agriculture Experimental and Research Station, Faculty of Agriculture, Moshtohor, Benha University, during 2012 and 2013 seasons to study the effect of spraying Mepiquate chloride (Pix) at 100, 200 and 250 mg/l, potassium citrate (K2) at 500 and 1000 mg/l and the combination of pix at 200 mg/l+ potassium citrate at 500 mg/l as foliar spray at 50, 70 and 90 days after sowing, on different growth and plant yield characteristics including fiber properties, minerals, carbohydrates and crude protein contents in the two cotton cultivars Giza 86 and Giza 88. The results showed that the different applied treatments increased growth characteristics, ie., leaf and branch number, total leaf area/plant, dry weight/plant and total chlorophyll (SPDS) in Giza 86 and Giza 88 cotton cultivars at 120 days after sowing during 2012 and 2013 seasons. Maximum increase was with pix at 200 mg/l+ potassium citrate at 500 mg/l in both seasons. Meanwhile plant height decreased with different applied treatments in the two assigned seasons. Also, Yield and yield components ie., bolls number and weight, seed cotton yield/plant and seed index significantly increased with different treatments and gave the highest value with pix at 200 mg/l+ potassium citrate at 500 mg/l in the two cultivars in both seasons. In addition, span length SL2. 5%, SL 50%, UR%, ML, UHM, UI%, SL66. 7%, Rd%, elongation and Strength. Fiber tests were increased with different treatments. On the other hand, different treatments decreased SFC%, CV%, b, MIC, CV%, Thin Places, Thick Paces and Neps in Giza 86 during 2012 and 2013 seasons. But, in Giza 88 the different treatments increased SL 50%, UR%, UHM, SL 66.7%, elongation, Mic. and Neps during 2012 and 2013 seasons. Different applied treatments decreased SL2, 5%, ML, UL%, CV% Rd, STR, CV%, Thin Places and Thick Places during 2012 and 2013 seasons. Furthermore, some minerals and bio constituents were increased with different applied treatments.