P-Aminophenol (PAP), a potentially toxic and mutagenic compound, is widely distributed in water and soil and has serious side effects on human health. This study presents a convenient, sensitive, and effective dual-signal assay for the detection of PAP in the environment. Two-dimensional manganese dioxide (MnO2) nanosheets were used as the carrier and quencher for fluorophore-labelled DNA to form a dual-signal nanoprobe, MnO2-DNA. Based on a specific redox reaction between the MnO2 nanosheets and target PAP, the corresponding absorption intensity of the product and the fluorescence intensity were both "turn-on" and also exhibited excellent correlation with the concentration of PAP. This strategy not only remarkably simplifies the detection process but also improves the reliability of results due to the dual-signal response, which has promising applications in environmental, clinical, and industrial research fields.