THIS STUDY was carried out at Sids Agricultural Research Station, Bani-Swef Governorate, Middle Egypt during the two successive seasons of 2014 and 2015, to study the effect of three plant spacings (15, 20 and 25 cm) and mepiquat chloride (MC) at three concentrations (50, 100 and 150 mg/l) on growth, productivity and quality of Egyptian cotton variety Giza 90. The treatments were arranged in the field using a split plot in a randomized complete block design with three replications, where plant spacings were the main plots and MC were the sub plots. Results showed that the widest plant spacing (25 cm) achieved an increase in dry weight/plant, leaf area/plant, number of fruiting branches/plant, earliness percentage, number of open bolls/plant, boll weight, seed cotton yield/feddan, seed index, lint percentage, leaf mineral elements percentage and photosynthetic pigments concentration and seed content of oil and protein. While, plant height, shedding percentage, days to first bud appearance, first open flower and crackle first boll were decreased. On the other hand, node number of the first sympodium and fiber properties were not affected by plant spacings. Spraying MC at the concentration of 150 mg/l led to increased for each of number of fruiting branches/plant, earliness percentage, number of open bolls/plant, boll weight, seed cotton yield/feddan, seed index, lint percentage, leaf mineral elements percentage and photosynthetic pigments concentration, seed content of oil and protein, micronaire reading, fiber strength and fiber elongation. While, dry weight/plant, leaf area/plant, plant height, shedding percentage, node number of the first sympodium, days to first bud appearance, first open flower and crackle first boll were decreased. On the other hand, fiber length and uniformity ratio were not affected by MC. The interaction between plant spacings and MC significantly affected all studied characters except node number of the first sympodium and fiber properties. From the above results, it could be concluded that grown plants on 25 cm with spraying MC at the concentration of 150 mg/l may be the best combination to improve the productivity of Egyptian cotton.