A field experiment was carried out to study the bioefficacy and phytotoxicity of oxyfluorfen (23.5% EC) in onion variety ‘Sukhsagar’ and its residual effect on the succeeding crop black gram variety ‘Basant Bahar (PDU-1)’ in Inceptisol of West Bengal. Pre-emergence application of oxyfluorfen 400 g/ha followed by one hand weeding (HW) at 30 days after planting (DAP) caused significantly lower weed density, weed dry weight and higher weed control efficiency at all the stages. Application of oxyfluorfen 200 g/ha + one HW at 30 DAP kept the weed density and dry weight below the economic threshold level and increased the bulb yield in onion. Though micro flora population at the initial stage was reduced due to application of herbicides but later their population was significantly higher than initial. Succeeding crop blackgram sown immediately after the harvest of onion was not affected by the residues of new formulation of oxyfluorfen at all different doses.