The exponential decrease of precipitation and increase of temperature in many dry regions in the world affect negatively the growth of main crops. The presence of associated weed species with these crops may add more adverse impact on yield. The present study aims at investigating the phytosociological structure of its associated wild species with rainfed barely (Hordeum vulgare L.) at Marsa-Matrouh Governorate, Egypt. Forty-eight stands were assigned at Marsa-Matrouh city for estimating the number of associated species with rainfed barely and its visual cover. Seventy-five species belonging to 63 genera and 24 families were recorded as associated species with rainfed barley. The most dominant families were Asteraceae followed by Poaceae, Chenopodiaceae, Fabaceae, Brassicaceae. A total of 48 species were recorded as annuals. On the other hand, 25 species were perennials. Two species were biennials. Therophytes were the dominant life form. The application of TWINSPAN on the cover estimates of 75 associated species recorded in the 48 sampled stands of barley, led to recognition of eight vegetation groups.The main indicator species for vegetative groups (1, 2, 3, 4, 5, 6, 7 and 8): Glebionis coronaria, Carrichtera annua, Elymus farctus, Erucaria microcarpa and Malva parviflora are native species at the Mediterranean coastal strip. Carrichtera annua-Erucaria microcarpagroup (VG 3) had the highest value of species richness. Moreover, Erucaria microcarpa- Vicia monantha (VG 6) showed the highest value of species turnover. Erucaria microcarpa- Vicia monantha (VG 6) showed the highest value of shannon index. Elymus farctus- Erucaria microcarpa (VG 5) showed the highest value of Simpson index. The present study will help in improving the understanding for the phytosociology of rainfed barely and will help in improving the agricultural practices to increase the yield of this plant under the prevailing harsh conditions.