Hydrogen peroxide (H2O2) is a significant biomarker in physiological processes. Abnormal levels of H2O2 are considered to be closely related to some acute diseases. Therefore, it is important to monitor the H2O2 levels in bio-samples. Herein, we present a novel non-enzymatic electrochemical H2O2 sensor based on the excellent electrocatalytic performance of a composite comprising Zn-Cr-Co ternary spinel metal oxide nanodots (ZnCrCoO4) anchored on the surface of nitrogen-doped carbon nanotubes (NCNTs), denoted as ZnCrCoO4/NCNTs, toward H2O2 reduction. ZnCrCoO4/NCNTs were synthesized using a facile one-pot hydrothermal strategy. The enhanced electrocatalytic performance of ZnCrCoO4 is resulted from the partial substitution of Co in spinel zinc cobaltate (ZnCo2O4) with Cr, which modifies the CoAO electronic structure and enhances electroconductivity. The ZnCrCoO4/NCNTs-based H2O2 sensor exhibited a wide quantitative detection range from 1 to 7330 lM with a detection limit of 1 mu M. The sensor showed excellent reproducibility and selectivity for H2O2 sensing. In addition, remarkable recoveries were obtained for H2O2-spiked fish serum samples. These results demonstrated that the as-developed sensor has a great potential in monitoring H2O2 levels in practical applications. (C) 2020 Elsevier Inc. All rights reserved.