The electrochemical and photochemical properties of graphene derivatives could be significantly improved by modifications in the chemical structure. Herein, reduced graphene oxide (RGO) was functionalized with l-arginine (l-Arg) by an amidation reaction between the support and amino acid. Deposition of a powerful ligand, l-Arg, on the optically active support generated an effective optical chemosensor for the determination of Cd(II), Co(II), Pb(II), and Cu(II). In addition, l-Arg-RGO was used as an electrode modifier to fabricate l-Arg-RGO modified glassy-carbon electrode (l-Arg-RGO/GCE) to be employed in the selective detection of Pb(II) ions by differential pulse anodic stripping voltammetry (DP-ASV). l-Arg-RGO/GCE afforded better results than the bare GCE, RGO/GCE, and l-Arg functionalized graphene quantum dot modified GCE. The nanostructure of RGO, modification by l-Arg, and homogeneous immobilization of resultant nanoparticles at the electrode surface are the reasons for outstanding results. The proposed electrochemical sensor has a wide linear range with a limit of detection equal to 0.06 nM, leading to the easy detection of Pb(II) in the presence of other cations. This research highlighted that RGO as a promising support of optical, and electrochemical sensors could be used in the selective, and sensitive determination of transition metals depends on the nature of the modifier. Moreover, l-Arg as an abundant amino acid deserves to perch on the support for optical, and electrochemical determination of transition metals.