Timing of defoliation and harvest can affect cotton yield and quality. Careful consideration of defoliating is necessary, because too early or too late defoliation may have a negative impact on yield potential and fibre quality. Therefore, field experiments were conducted during 2011 and 2012 to determine the effects of defoliation and harvesting timing of an early maturing and a medium-late maturing cotton cultivar for identifying ideal time of application to realize high productivity and fibre quality. The experiment was conducted in the split-split plot arrangement with three replications. Cultivars were the main plots (DP 499, and SG-125), defoliation times were the sub-plots (50 (early), 70 (mid), and 90 (late) percent open boll), and harvest times were the sub-sub plots (pickings at two and four weeks after defoliation treatments). The result revealed that yields of the early harvest at late defoliation timing and late harvest at mid defoliation timing were significantly higher than the yields of all other treatments both in 2011 and 2012. When the cotton crop was defoliated at 70% open boll, early harvest produced the longest fibre in 2011. Early harvest at early defoliation and late harvest at mid defoliation treatments produced the finest fibres. The largest strength value was observed for cotton defoliated at 70% open boll. On the basis of these results it is suggested that defoliation at 90% open boll for early maturing cultivar and defoliation at 70% open boll for medium-late maturing cultivar could be recommended for higher yields without undesirable changes in fibre quality.