Field experiment was conducted at the Teaching and Research Farm of Ambrose Alli University, Ekpoma, Edo. State, Nigeria to the evaluate influence of some pre emergence herbicides application on weed flora and nutritional composition of cowpea grains. The treatments consisted of no weeding (control), Coda goldÒ at 1.65 kg a.i./ha, Galex at 3.0 kg a.i./ha, Pendilin at 2.0 kg a.i./ha, One hoe weeding at 3 weeks after planting (WAP) and Two hoe weeding at 3 & 7WAP laid out in a Randomized Complete Block Design (RCBD) with four replicates. The result showed that there were changes in weed flora composition of broadleaved weeds and grasses except sedges before and after experiment. For instance, approximately 52.38% of the weeds were broadleaved species and 28.57% were grasses before planting while about 38.1% of the weeds were broadleaved species and 42.86 % grasses after harvest. Before planting, annual weed species were 28.57% and perennial 71.43% while after harvest, annual weed species were 47.62% and perennial 52.39%. The result further showed that plot treated with herbicides had a slight increase in nutritional composition of cowpea grains when compared to hoe weeding and no weeding. Since, the herbicides used in the study altered weed flora composition of cowpea plant without having any adverse effect on the nutritional composition of the grains, they are recommendable to farmers for boosting cowpea production in Nigeria. Keywords: cowpea grains, nutritional composition, pre emergence herbicides, weed flora, DOI: 10.7176/JBAH/9-2-0