One field experiment was carried out on clay soil in 2016 season and repeated in 2017 season in El-Gemmeiza Agricultural Research Station, Agricultural Research Center, El-Gharbiya Governorate, Egypt, to study the effect of seven treatments including foliar application with two rates of mepiquat chloride (pix); 2 and 3cm³/L, two rates of  Kaolin (2 and 3g/L), two rates of mepiquat chloride(pix) and Kaolin application in combination (2cm³+2g)/L, (3cm³+3g)/Lthree times (at squaring stage, at the start of flowering and at the top of flowering) and control treatment on leaf chemical composition, plant growth, earliness, fiber quality and yield of Egyptian cotton (Gossypium barbadense L.), Giza 86 cultivar. A randomized complete blocks design with 3 replicates was used in both seasons. The important results could be summarized as follow:-  The tested treatments had a significant effect on leaves N, P, K, chlorophyll a, b, total chlorophyll and carotenoids contents in the two seasons of study, where foliar application with mepiquat chloride at 3cm³/L in combined with kaolin at 3g/L three times recorded the highest values of these traits in both seasons followed by foliar application with mepiquat chloride alone at 3cm³/L. While, the control treatment produced the lowest values of these traits.Foliar spraying with mepiquat chloride at 3cm³/L in combined with kaolin at 3g/L three times significantly reduced final plant height, followed by foliar application with mepiquat chloride at 3cm³/L three times, foliar application with mepiquat chloride at 2cm³/L in combined with kaolin at 2g/L three times, foliar application with mepiquat chloride at 2cm³/L, foliar application with kaolin at 3g/L three times and foliar application with kaolin at 2g/L three times, while control treatment recorded the tallest plants. Number of fruiting branches/plant did not affect by these treatments. Foliar spraying with mepiquat chloride at 3cm³/L in combined with kaolin at 3g/L three times significantly increased numbers of total flowers and total bolls set/plant, boll setting and earliness percentages followed by foliar application with mepiquat chloride at 3cm³/L. But, the lowest values were obtained from the control treatment.Foliar spraying with mepiquat chloride at 3cm³/L in combined with kaolin at 3g/L three times significantly increased boll weight, number of open bolls/plant, seed cotton yield/plant, seed index and seed cotton yield/fed in the two seasons of study followed by foliar application with mepiquat chloride at 3cm³/L. But, untreated plants produced the lowest values.On the other hand, the tested treatments had insignificant effect on fiber quality (fiber strength and micronaire reading) and lint percentage in both seasons.This study demonstrates that foliar spraying with mepiquat chloride (pix) at 3cm³/L in combined with kaolin at 3g/L three times (at squaring stage, at the start of flowering and at the top of flowering) could be recommended to improve the chemical composition of leaves, vegetative growth traits, earliness, yield/feddan, yield components and  fiber quality of Giza 86 cotton cultivar under conditions of El-Gemmeiza location.