Among the sedges Fimbristylis are considered as very problematic weed in both irrigated and non irrigated rice ecosystems as it was reported to reduce rice yield by 9-43%. This work was undertaken, in 2014 and 2015, to assess the status of Fimbristylis species in transplanted Kharif rice at Jorhat district, Assam. Weed flora was surveyed following standard weed survey protocol. A taxonomic key for identification of these 5 taxa was developed for their easy reorganization in field condition. The moderately deep rooted problematic weed F. bisumbellata recorded in East Jorhat, Ujoni Majuli, Kaliapani, Titabar and Central Jorhat developmental blocks, as one of the most problematic weeds of upland autumn rice and other field crops of marshy situation during summer season. High frequency and population density of Fimbristylis species may be attributed to suitability of agro-climatic condition of Jorhat district for their growth and development and their occurrence has always caused yield reduction in rice due to higher magnitude of competition for nutrient and space in addition to its allelopathic effect on rice.