The low activity of nanozymes, which work as an alternative to natural enzymes, limits their applications in the fabrication of biosensors, drawing increasing attention aimed at improving their catalytic capacity. In this work, the peroxidase-like activity of MoS₂nanosheets (NSs) was dramatically enhanced through DNA modification, and was 4.3-times higher than that of bare MoS₂NSs. Such an enhancement of catalytic activity was mainly ascribed to the increased affinity of the DNA/ MoS₂NSs toward the substrate, TMB, further accelerating electron transfer from TMB to H₂O₂. On the basis of DNA-tuned MoS₂NS nanozyme activity, a colorimetric sensing platform was developed for the facile detection of carcinoembryonic antigen (CEA) in a sensitive manner. Interestingly, a convenient, affordable, and instrument-free portable test kit was fabricated to visually monitor CEAviarooting the aptamer/ MoS₂NS system into an agarose hydrogel. Importantly, our work illuminates the feasibility of using DNA to enhance the catalysis of nanozymes and their application potential in the label-free, portable, and visual detection of aptamer-targeted biomolecules.