Display omitted •Novel graphene-chitosan-silver composite for lead sensing.•Self-reduction of Ag2+ and anchoring of silver nanoparticles on the surface of GO-CS.•Surface silver nanoparticles offer selective lead sensing with superior sensitivity.•The developed sensor used for detection of lead in contaminated water. Owing to the adverse effect of lead (Pb) on almost every organ of the body and predominantly, the nervous system, a sensitive and selective detection of the lead below the permissible limit is highly desirable. In the present work, an electrochemical lead sensor based on graphene oxide-chitosan (GO-CS) biocomposite, surface functionalized with silver nanoparticles has been demonstrated. The GO-CS biocomposite formation is ascribed to the hydrogen bonding and electrostatic interaction between the oxygen-containing functional groups of GO and chitosan. The amide and carboxyl groups present in GO-CS helps in the reduction of Ag2+ and anchoring of the silver nanoparticles (Ag0) on the surface. This eventually resulted in the enhanced electrochemical activity and charge transfer thereby facilitating selective chemisorption of Pb(II) on GO-CS-Ag. The sensor exhibited superior response with limit of detection (LOD) of 0.15 ppb and a linear detection range from 0.2 to 40 ppb (MRL = 10 ppb). Importantly, the sensor is highly selective towards Pb(II) with selectivity factor ranging from 5 to 8, as compared with other heavy metal ions. The developed sensor has been tested and validated for lead detection in contaminated water samples wherein the results were found to be in agreement with those from atomic absorption spectroscopy (AAS) analysis.