Roundup-ready cotton was tested under confined field trials at NaSARRI-Serere in Eastern Uganda and Mubuku Prison Farm- Kasese, Western Uganda for the first time during the 2009/2010 and 2010/2011 cotton seasons. Weeds were controlled using two dosages of Roundup. These were the recommended rate and twice the recommended rate applied to transgenic cotton once or twice. The recommended rate was applied at 220 mls/15 litres of water, while the double rate was applied at 440 mls/15 litres. For the BPA 2002 control commercial variety, weed control was done through hand weeding three times. Major weeds of cotton were fully controlled by herbicide application at the two rates applied twice on the transgenic cotton without any negative effect to the cotton crop. At NaSARRI during the second season, application of the recommended rate of roundup twice to variety SG 125RRFlEX gave seed cotton yields of 1015.6 kg/ha, compared to 1265.6 kg/ha when the rate was doubled and applied twice. The local commercial variety BPA 2002 hand weeded three times during the same season yielded 1495.6 kg/ha. The results point to the prospective success of herbicide use on transgenic cotton under Ugandan conditions and strengthen the need for introgression of the technology to the local cotton varieties in the country.