A long-term field experiment from 1999-2000 to 2015-16 at CCS Haryana Agricultural University, Regional Research Station, Karnal, Haryana, India was done to study the effect of green manuring and continuous or rotational use of herbicides on weeds and productivity of the rice-wheat cropping system. Based on data from 2008-09 onward, the density of grassy weeds in the weedy plots under green manuring (GM) (7-37 plants/m2) remained lower or equal to treatments without green manuring (WGM) (6-37 plants/m2) in rice with few exceptions. Similarly, broad-leaf weeds (BLW) and sedges under GM (0-83 plants/m2) remained lower or similar to WGM (0-106 plants/m2) across different years. In wheat, the density of Phalaris minor was higher or similar under GM (55-229 plants/m2) than WGM (45-177 plants/m2), while the converse was true for BLW (19-275 plants/m2 and 45-405 plants/m2, respectively). The most dominant weed Echinochloa crus-galli in rice and Phalaris minor in wheat did not develop any envisaged sign of herbicide resistance against continuous and rotational used herbicides in respective crops. Grain yields of rice under weed-free situations were better under GM (6.37-8.30 t/ha) than WGM (5.59-7.63 t/ha). Similarly, the grain yields of wheat were higher under GM (5.25-5.99 t/ha) than WGM (5.08-5.54 t/ha). Consequently, the overall system productivity was better under GM.