The International Agency for Research cancer (IARC) has classified nitrite in Group 2A of probable carcinogens to human. Herein, we report on the rapid and selective colorimetric detection of nitrite using a chemically modified gold nanoparticle (AuNP)-cerium oxide (CeO₂) NP-anchored graphene oxide (GO) hybrid nanozyme in a catalytic colorimetric assay where nitrite acts as the main oxidant/target analyte and 3,3′,5,5′-tetramethylbenzidine (TMB) as the substrate. CeO₂ NPs and GO were synthesized separately and incorporated in-situ, in a synthetic solution involving the chemical reduction of Au salt to AuNPs. The chemical modification process aided the adsorption of CeO₂ NPs and AuNPs on GO nanosheets, yielding a highly catalytic AuNP–CeO₂ NP@GO nanohybrid material. Under optimum experimental conditions, a novel colorimetric assay for nitrite recognition was constructed in which AuNP–CeO₂ NP@GO hybrid nanozyme catalysed the oxidation of TMB in the presence of nitrite prepared in a 2-(n-morpholino)ethanesulfonic acid-2-[bis(2-hydroxyethyl)amino]-2-(hydroxymethyl)propane-1,3-diol-tris(hydroxymethyl)aminomethane acetate (MES-BIS-TRIS-Trisma Ac)-citric acid buffer solution, pH 2. Nitrite was quantitatively detected in a concentration dependent manner from 100 μM to 5000 μM with a correlation coefficient of 0.9961 and a limit of detection of 4.6 μM. Selective detection of nitrite was confirmed by the generation of a unique green colour reaction upon nitrite interaction in the AuNP–CeO₂ NP@GO hybrid nanozyme redox cycle with TMB. None of the several tested metal ions and including H₂O₂ yielded a positive colour response, thus demonstrating the superior selectivity of the catalytic colorimetric assay for nitrite recognition. The AuNP–CeO₂ NP@GO hybrid nanozyme catalytic colorimetric assay was successfully applied in the detection of nitrite in tap water.