Blackgram (Vigna mungo (L.) Hepper) is one of the most remunerative legume crop which grown in Kharif or summer season. An experiment was conducted to evaluate the activity and selectivity of the post-emergence herbicide haloxyfop on weeds growth and blackgram productivity during Kharif season of 2015 and 2016 at N.E. Borlaug Crop Research Centre, G.B.P.U.A& T, Pantnagar, Uttarakhand. The  grass weeds: Echinochloa colona (15.5 and 15.0%), Eleusine indica (48.6 and 32.3%), Dactyloctenium aegyptium (18.3 and 22.0%), Digitaria sanguinalis (3.5 and 6.4%), Brachiaria spp. (2.8 and 3.3%) and Panicum maximum (11.3 and 21.0%) dominated the field (during 2015 and 2016, respectively).The lowest weed density and biomass, and highest weed control efficiency and blackgram seed yield were recorded with post-emergence application (PoE) of haloxyfop  135 g/ha followed by and at par with its lower dose (108 g/ha) during both the years and  statistically at par with standard check quizalofop-ethyl 50g/ha, only during 2015. No phytotoxicity occurred to blackgram on 1, 3, 5, 7, 10, 15 and 30 days after application at any of the tested haloxyfop doses and was found safe for growing succeeding transplanted rice as rice growth and yield were not affected by any of the doses of haloxyfop.