The present work aimed to study the floristic diversity and vegetation analysis of weeds associated with Opuntia ficus indica (L.) Mill. in three Nile Delta governorates. Ninety nine stands (10m X 10m) were surveyed in autumn and spring (2015)(2016). Seventy one species belonging to 61 genera and 27 families were recorded associated with Prickly Pear. Poaceae, Asteraceae, Chenopodiaceae and Brassicaceae, were the most dominant families. Annuals recorded the highest number of species (45 species) while perennials were represented by 26 species. Therophytes were the dominant life form represented by 43 species while monoregional represented the dominant floristic category (22 species). The application of TWINSPAN on the cover estimates of 71 associated species recorded in the 99 sampled stands of Prickly Pear, led to the recognition of 8 vegetation groups: The names of these groups are: A: Boerhavia Coccinea, B: Cynodon dactylon, C: Cyperus rotundus, D: Psidium guajava, E: Amaranthus lividus, F: Malva parviflora, G: Phragmites australi and H: Imperata cylindrical. M. parviflora group had the highest value of species richness (21.6 species/stand) and relative evenness (0.63), while the highest species turnover (8.2) was recorded in Boerhavia coccenea VG A and the highest relative concentration of dominance (2.43) was recorded in Amaranthus lividus VG E. Some of the recorded species are invasive and negatively impact Prickly Pear cover, these species need control. Some other species provides many ecological and human services, these species need management and conservation.