This dataset includes estimates of herbaceous aboveground biomass (AGB) for the Atchafalaya and Terrebonne basins of the Mississippi River Delta in coastal Louisiana, USA, for the fall and spring seasons of 2021. AGB, estimated as dry biomass in g per square meter, was estimated from BRDF-adjusted surface reflectance products from NASA's Next Generation Airborne Visible Infrared Imaging Spectrometer (AVIRIS-NG) acquired over the study area in April and August 2021. BRDF-adjusted reflectance was derived from hemispherical-directional surface reflectance with atmospheric correction. An empirical model to estimate AGB was generated by comparing local pixel reflectance spectra with coincident in-situ samples of herbaceous vegetation AGB. This model was then scaled to the AVIRIS-NG mosaic imagery to map herbaceous AGB across the Atchafalaya and Terrebonne Basins. The Delta-X campaign conducted both airborne (remote sensing) and field (in situ) measurements to measure hydrology, water quality (e.g., total suspended solids (TSS)), and vegetation structure. These data serve to better understand rates of soil erosion, accretion, and creation in the delta system, with the goal of building better models of how river deltas will behave under relative sea level rise. The data are provided in cloud optimized GeoTIFF (COG) format.