Cyperus rotundus is a troublesome perennial weed of kharif season. In maize, it is not controlled with the already recommended herbicide i. e. atrazine 50 WP. All the three formulations of 2,4-D i. e. sodium, di-methyl amine and ethyl ester were applied as post-emergence on C. rotundus infested crop of maize from 2007 to 2009 as blanket spray after the pre-emergence application (20-25 DAS) of atrazine 1.0 kg/ha. Out of the three formulations, post-emergence application of 2,4-D di-methyl amine at 0.44, 0.58 and 0.73 kg/ha was found more effective for controlling C. rotundus as compared to other formulations i. e. sodium and ethyl ester. All the three formulations showed no adverse effect on plant growth and produced grain yield of maize statistically similar to each other. On an average of three years, post-emergence application of 2,4-D di-methyl amine at 0.44, 0.58 and 0.73 kg/ha increased maize grain yield significantly over unweeded control and all these treatments produced 23.8, 31.1 and 26.7% higher yield than unweeded control treatment, respectively.