Owing to the importance of the correct selection of the synthesis parameters when fabricating nanoparticles, a general full factorial design with three factors: pH, thioacetamide/CuCl $$_2{\cdot}$$ 2 · H $$_2$$ 2 O ratio, and stirring time was performed to find the factors affecting the spectral position of the near-infrared (NIR) absorption band of CuS nanoparticles. Based on the results, there is evidence that the peak position depends on one significant interaction, as well as on two main factors. Additionally, taking into account $$R^2$$ R 2 , we argue that the variability of the wavelength corresponding to peak position of the NIR absorption band can be explained by a linear model with an accuracy above 93%.