Continued application of the same chemicals as herbicides could develop resistance of weeds to the herbicides. Hence, screening of newly developed herbicide formulations is essential to find out more effective herbicides for controlling weeds in sugarcane at different growth stages of the crop and the weeds. An experiment was conducted to find out the efficacy of a new herbicide formulation, Diuron 46.8 % + Hexazinone 13.2 % (DI+HEX), in controlling weeds in sugarcane as a pre-emergent and early-post emergent application. The identification of the effective dosage of the chemical in the observational field experiment and the replicated field experiment of controlling weeds were done at the Sugarcane Research Institute, Uda Walawe in 2016/17. Apilot project of application of effective dosage of DI+HEX in 0.5 ac of sugarcane field was conducted in a farmer’s field at Lanka Sugar Company (Pvt) Ltd, Sevanagala. The effect of DI+HEX on weed knock-down, residual activity, and phytotoxicity on sugarcane was evaluated in all experiments. It was identified that the application of a new herbicide formulation, DI+HEX, at the rate of 3.0 kg/ha is effective and better than the application of recommended herbicide, Diuron 80 WP, at the rate of 3.5 kg/ha in controlling grass and broadleaved weeds at the pre-emergent stage. However, DI+HEX is not effective in controlling sedges, particularly Cyperus rotundus. Therefore, the application of DI+HEX at the rate of 3.0 kg/ha mixed with 400 litres of water at the pre-emergent stage is recommended to control grass and broadleaved weeds in sugarcane.