Abstract The species identification, distribution pattern, density and biomass of salt marsh and seagrass plants with some of the ecological parameters were studied in the Bakkhali river estuary, Cox's Bazar, Bangladesh during the first half of 2006. Two salt marsh species ( Spartina sp. and Imperata cylindrica ) and one seagrass species ( Halophila beccarii ) were identified during this investigation, providing the first reports of Spartina sp. and H. beccarii in coastal Bangladesh. Seagrass H. beccarii was found in an accreted area and co-existing with salt marsh, and scattered sparsely in the salt marsh habitat and macroalgae Ulva intestinalis . Flowering and fruiting were recorded from the seagrass H. beccarri during January and February. No flowers and fruits were observed for the salt marsh Spartina sp. during the study period. Results showed that the shoot density of Spartina ranged from 400 to 2875 shoots m −2 with the highest total biomass (165.80 g dry weight (DW) m −2 ) in March. Shoot density of H. beccarii ranged from 2716 to 14320 shoots m −2 in this estuarine coastal environment. The total biomass of seagrass was higher (17.56 g DW m −2 ) in March compared to the other months. The highest H. beccarii above ground (AG) biomass and below ground (BG) biomass were 9.59 g DW m −2 and 9.42 g DW m −2 , respectively. These parameters are comparable with those generally observed for the salt marsh and seagrass species in the other places of the world.