In this study, a novel 4,4'-diaminostilbene-2,2'-disulfonic acid (DASDSA)-functionalized reduced graphene oxide (DASDSA-rGO) was prepared via simple refluxing method involving GO and DASDSA in the presence of ammonia solution followed by reduction with hydrazine hydrate. FTIR spectroscopy, Raman scattering, X-ray photoelectron spectroscopy (XPS), and XRD analyses confirmed the successful functionalization and reduction of GO in DASDSA-rGO. The FTIR and XPS analyses also confirmed covalent bond formation between DASDSA and graphene. The DASDSA spacer successfully minimized the restacking of rGO sheets as observed from FESEM analysis. Several redox transition states and -SO3H groups of grafted DASDSA moieties provided excellent pseudocapacitance performance of the DASDSA-rGO electrode. The DASDSA-rGO electrode showed high specific capacitance (C) value of 1042 F g(-1) at a current density of 1 A g(-1), good cycling stability (95% capacitance retention after 3000 cycles), and excellent rate capability in a three-electrode setup. The DASDSA-rGO (positive electrode) and rGO (negative electrode) were assembled to prepare an asymmetric supercapacitor (ASC) device. The power density values of the ASC device were calculated to be 650 and 7800 W kg(-1) at energy density values of 37.37 and 23.78 W h kg(-1), respectively. The ASC device exhibited C value of 159 F g(-1) at 1 A g(-1) and displayed 86% retention in C after 8500 cycles. The EIS data of the three-electrode system and ASC device were fitted with Z-views to determine the different resistance components after a different number of charge-discharge cycles in a cycling stability test.