In this study, silver- and copper-decorated carbon dots (Ag-CDs and Cu-CDs) with strong absorption in the near-infrared (NIR) region were successfully synthesized using a simple chemical approach, and their potential for cancer treatment through photothermal therapy was investigated. The structural characteristics and in vitro photothermal performance of the synthesized nanomaterials were systematically evaluated. To characterize the structural and optical properties of the Ag- and Cu-decorated carbon dots, X-ray diffraction (XRD), transmission electron microscopy (TEM), elemental analysis, and Fourier-transform infrared spectroscopy (FTIR) were employed. An 808 nm laser with a power density of 1 W cm⁻² was used as the irradiation source. The results of all characterization techniques confirmed the successful formation of the synthesized nanostructures, and the average size of the carbon dots was found to be below 50 nm. Furthermore, the amounts of silver and copper nanoparticles used for surface decoration were optimized to achieve the highest photothermal response. Following laser irradiation, the Ag-decorated and Cu-decorated carbon dots exhibited temperature increases of 15.9 °C and 12.3 °C, respectively, and were therefore selected as the optimum samples. Owing to their excellent photostability, favorable biocompatibility, and enhanced photothermal performance, the synthesized Ag- and Cu-decorated carbon dots can serve as effective photothermal agents. Moreover, the use of a relatively low laser power density (808 nm, 1 W cm⁻²) further highlights the suitability of these nanostructures for in vitro photothermal therapy applications. These findings demonstrate that metal-decorated carbon dots are promising candidates for efficient photothermal cancer treatment.