Twenty four water samples were collected and analyzed for DOC and optical properties to characterize the origin and fate of DOM (dissolved organic matter ) along the land and coast continuum in the Sundarban mangrove of Bangladesh. High levels of dissolved organic carbon (DOC) are associated with a highly complex and aromatic character with SUVA254 of 7.13-45.05 L mg-C-1 m-1. Excitation-emission matrix (EEM) of DOM was analyzed by the parallel factor analysis (PARAFAC); and three different allochthonousfluorophore groups and one autochthonous fluorophore group were identified. Intensive weathering coupled with anthropogenic activities in the catchment area supplied a large amount ofvarying chemistry of allochthonous DOM into the Sundarban mangrove. Emission wavelength bands at particular excitation wavelength were used to estimate Fluorescence Index (FI, 1.38-1.74), Biological/Autochthonous Index (BIX, 0.58-0.72) and Humification Index (HIX, 2.23-4.68), exemplify that fresh and labile DOM from terrestrial sources regulate the carbon cycling in the Sundarban mangrove.