Most of the farmers shifted to direct-seeded rice (DSR) from conventional puddled-transplanted system. One of the major challenges in DSR is weed management, which reduces the productivity of the rice system significantly. Therefore, many herbicide combinations are being tried for broad-spectrum control of weeds. In the present study, field experiments were conducted during Kharif 2013 and 2014 to know the herbicides efficacy when used in mixture using dose-response curve in DSR. The treatments comprised of tank-mix combinations of two herbicides viz. fenoxaprop (0, 30, 40, 50, 60 g/ha) and metsulfuron (0, 2.5, 3.0, 3.5, 4.0 g/ha) to control grassy and broad-leaved weeds, respectively in DSR. Among many non-linear dose-response models, hill model was found to be the best for the data. Results revealed that when fenoxaprop applied in mixture with metsulfuron, its efficacy increased/decreased 4-5% during both the years. Further, when metsulfuron was applied in mixture, its ED50 value was increased from 3.43 to3.62 g/ha as compared to its alone application. Thus, the study revealed the presence of antagonistic effect of fenoxaprop on metsulfuron when used in mixture, which ultimately resulted in reduced efficacy in terms of pre cent weed control.