The present study demonstrates utilization of functionalized seaweed polysaccharide, namely agarosegallate (Ag-GA Est ) for the preparation of reduced graphene oxide (rGO) under mild reaction conditions. Ag-GA Est obtained with the lowest degree of substitution (degree of substitution (DS) = 0.45; with 1 : 0.5 w/w agarose : gallic acid) shows excellent performance compared to its high DS (1.1; with 1 : 2.0 w/w agarose : gallic acid) ester derivatives. Further, the formation of rGO was confirmed using UV-Vis, TEM, FTIR, Raman spectroscopy, elemental and XRD analysis. This study describes a new application of seaweedderived polysaccharides.