© 2021 Elsevier B.V.This study discussed the simultaneous electrochemical detection of highly toxic Pb2+, Cu2+, Hg2+ heavy metals by the Co3O4 modified electrode. The Co3O4 nanocubes (Co3O4-NC) are prepared by the facile hydrothermal synthesis route which produces highly crystalline particles without an annealing process. The structural properties are characterized by XRD, Raman, XPS, FESEM, and HRTEM analysis. The SAED pattern endorses the single-crystalline nature of Co3O4-NC. The prepared material was subjected to detect the heavy metals electrochemically via DPV techniques. The Co3O4-NC/SPCE revealed good electroanalytical activity towards both individual and simultaneous detection of heavy metals. The developed heavy metal sensor exhibited good sensitivity (16.73 ± 0.8 µA µM−1 cm−2 for Pb2+, 11.46 ± 0.5 µA µM−1 cm−2 for Cu2+, and 16.86 ± 0.7 µA µM−1 cm−2 for Hg2+) and LOD (4.1 ± 0.2, 0.9 ± 0.04, 0.1 ± 0.005 nM for Pb2+, Cu2+, Hg2+, respectively) in the simultaneous detection. Moreover, the Co3O4-NC/SPCE exhibited high selectivity with the other potential interfering metal ions and nitro compounds in tap water and pond water samples. Additionally, the Co3O4-NC/SPCE reveals good recoveries of about 100–101.5% for tap water and 97–101% for pond water samples. Hence, our proposed Co3O4-NC/SPCE is a good electrode material for the determination of toxic heavy metal pollutants in real-time monitoring sensor devices.