Given their hazardous effects on the environment and human health, the monitoring of pesticide residues is recognized as the most effective means to guard food and public safety. Oxidoreductase-type nanozymes (peroxidase and oxidase) have been widely employed to develop optical methods for pesticide detection, but these methods are susceptible to matrix redox interference and lack detection specificity for intended targets. To overcome the above deficiencies, here we designed a novel organophosphorus hydrolase-mimicking nanozyme, namely, nanosized ceria capped by Ca²⁺-chelated 2-aminoterephthalic acid (Ca-ATPA@CeO₂) featuring stable fluorescence and dual-site-empowered high catalytic activity, to enable the exclusive dual-mode detection of hypertoxic methyl-paraoxon (MP). The synergy of hard Lewis acid Ca²⁺ and nanoceria creates dual active sites that jointly promote the binding and hydrolysis of MP to yellow p-nitrophenol (pNP) specifically. Meanwhile, the generated pNP quenches the intrinsic fluorescence of Ca-ATPA@CeO₂ via the inner filter effect. As a result, dual-mode colorimetric and fluorescence determination of MP was achieved using the designed versatile nanozyme. The alliance of excellent target catalytic specificity and bimodal cross-check characteristic enables accurate quantification of the individual pesticide in complex matrices. Our work introduces a new reliable strategy for MP selective detection that can avoid potential interference from redox substances.