Bidens pilosa L. is an Asteraceae plant that originated from South America and can be found in the most countries of tropical and subtropical regions. The present study aimed to identify the flora and vegetation groups associated to the noxious species, B. pilosa to show its effect of the native flora. A 231 stands distributed in 5 governorates located at Nile Delta were used to identify the associated flora and vegetation groups with B. pilosa populations. Floristic analysis showed 113 species associated with Bidens pilosa L. It was found that family Poaceae had the highest number of associated species with B. pilosa (25 species), also Therophytes were the dominant life form represented by 78 species (69.03% of the total species) and the annuals were recorded 70% of the total species. A 39 species representing 34.5% of the total species have environmentally service as segetals. A 68 species = 60.2% of the total recorded species have economic goods as medicinal plants. The application of TWINSPAN on the cover estimates of 113 associated species recorded in the 231 sampled stands of B. pilosa, lead to the recognition of 13 vegetation groups. These groups showed a reasonable segregation along the habitats DECORANA. The vegetation groups are named according to first and second dominant species associated with B. pilosa. The presence of B. pilosa 100% in all vegetation groups, while cover varied from one group to another. Increase in the cover of B. pilosa weed reduced the number of associated species. So, Bidens pilosa plant effects on the native weed flora in the Nile Delta region. Therefore, B. pilosa weed must be controlled to conserve the native flora.