The hexavalent Chromium (Chromium (VI) (or) Cr6+) is considered as the most toxic element that directly affects the environment and the human cycle adversely. Therefore, in the present study we proposed a sensitive and selective electrochemical sensor for the detection of Cr6+ in various water samples using graphene carbon nitride decorated with silver molybdate immobilized with nafion (g-C3N4/AgM/Nf) modified glassy carbon electrode (GCE). The nanocomposite was synthesized by sonochemical method and characterized by various analytical and spectroscopic techniques. The g-C3N4/AgM/Nf/GCE was exceptional and showed massive electrocatalytic change via the appearance of peaks in amperometric i-t technique. Cr6+ has a reduction peak appearing at 0.1-0.7 mu M, with a low limit of detection of 0.0016 mu M, and sensitivity of 65.8 mu A mu M(-1)cm(-2). The g-C3N4/AgM/Nf/GCE sensor for Cr6+ exhibited a good selectivity, stability, sensitivity, and reproducibility, which certified that the g-C3N4/AgM/Nf/GCE is a promising electrode. The electrochemical sensing method also accessed for the recognition of Cr6+ in different water samples and showed good feasibility with superior recovery. (C) 2020 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.