Majority of the deep-water rice area along the Brahmaputra Valley in Assam represents typical ecotone zone between the hydrophytic and terrestrial ecosystems, and thus the crop-weed competition environment is different from that of terrestrial land. Keeping this in view, a study was undertaken during 2022 and 2023 in the Brahmaputra ecotone of greater Majuli district of Upper Brahmaputra Valley Agro-climatic zone of Assam. The objective was to study the weed flora composition and weed dynamics in deep water rice in the Brahmaputra ecotone in different land situations. The study was conducted by random plotting of one square meter quadrats in the areas along the river in three distinct situations, viz, i. Temporary River Island (TRI) of Dhodang chapori, ii. Permanent River Island (PRI) and iii.  Permanent River edge (PRE) of Dhodang- Ujjirati. The climate of the study area is subtropical with a hot-humid summer, heavily showered monsoon and a mild-moderate winter. The soil nutrient content was moderately rich. Sixty weed species were observed during entire cropping period of this study in TRI, out of which 10 species were invariably present from crop growth stage (CGS) 1 to 3. In PRI and PRE, 67 and 49 weed species, respectively, were observed. Cynodon dactylon was found to be the most successful weed species and was dominant in the fields from pre- to post monsoon situations and it showed very strong association with Arundo donax. In temporary islands, no strong weed-species association was detected. However, in permanent edge ecotone zone, Cyperus difformis had strong negative association with Eleocharis geniculata and Cynodon dactylon, followed by Alternanthera philoxeroides. The permanent river islands and temporary islands were dominated by grasses, whereas sedges were dominant in permanent edges. The number of species and weed biomass revealed very strong correlation with Margalef’s species richness index, Pielou’s evenness index and Shannon and Wiener’s diversity index. However, the correlations of all the diversity indices with soil pH, available N, P and K, were found to be weak to very weak. The results of weed flora association study reflected the increasing community relatedness as TRI> PRE > PRI, which might be due to the presence of least disturbance in soil, cropping, and resource availability in permanent islands in comparison to other land situations.