Remote sensing technique has been used to estimate seagrass biomass over large areal coverage to avoid costly and time consuming. Nevertheless, the existing remote sensing methods only reported the density coverage estimations. As such, the absolute seagrass biomass and its distribution still remain unquantified. Subsequently, in this paper, we introduced a new approach for seagrass biomass determination to report the distribution and its absolute quantification using remote sensing technique. Two-step data processing of satellite remote sensing data was performed, namely: (i) detection and mapping of seagrass occurrence; and (ii) determination of seagrass biomass. The first step processing involves the retrieval of substrate-leaving radiance, whilst the latter modeled the in-situ dry weight samples against the corresponding satellite reflectance after undergone the first step data processing. The newly launched Landsat-8 Operational Land Imager band 2, 3 and 4 were used and applied in Merambong Shoal and vicinity that have various density of seagrass coverage. The results indicated good agreement with in-situ verifications. The seagrass occurrence areas were classified at 78.17 % overall classification accuracy (khat statistics=0.87; and total aboveground seagrass biomass in 5.677 ha area of Merambong Shoal for May 2013 was determined as13.020 kg, with average of 2.293 kg ha -1 and accuracy (RMSE) at± 1.75 g m -2 .The new approach introduced is found very sensitive for detrimental changes in seagrass biomass, thereby offers an opportunities envisage as indicator for changes in such related environments. Importantly the approach can be expandable to other substrate features, hence contributing new inputs for coastal ecology as a whole.