<p>Cadmium (Cd²⁺), which is a highly toxic heavy metal pollutant with severe health and environmental implications, demanding the development of rapid, cost-effective, and selective, one pot detection strategies. In this work, we report the synthesis of two-dimensional molybdenum diselenide (MoSe₂) nanosheets via liquid-phase exfoliation and its application as a peroxidase-mimicking nanozyme and for the first time, pristine MoSe₂ nanosheets are employed for the colorimetric detection of Cd²⁺ ions. The structural and optical characterization of exfoliated MoSe₂ nanosheets was confirmed by X-ray diffraction (XRD), Field effect scanning electron microscopy (FESEM), Transmission electron microscopy (TEM) Raman spectroscopy, and UV–Vis absorption spectroscopy, which confirmed few-layer exfoliation. The exfoliated MoSe₂ nanosheets exhibited pronounced peroxidase-like activity and we have studied distinct changes in vibrational features after MoSe₂ and Cd²⁺ ions incorporation, evidencing their role in catalytic activity and Cd²⁺ binding. Cd²⁺ ions were selectively detected using 3,3′,5,5′-tetramethylbenzidine (TMB) as the chromogenic substrate, achieving a detection limit of 0.047 ppm. These results highlight the potential of MoSe₂ nanosheets as a robust, portable, and cost-effective sensing platform for real-time environmental monitoring of cadmium contamination.</p> Graphical abstract <p></p>