Cotton fabric samples were treated with copper acetate mordant, in addition to green synthesized copper nanoparticles extracted from the Conocarpus erectus leaves, with two different concentrations of 10% and 20%, respectively. Two dyeing techniques, continuous dyeing and exhaust dyeing, were employed. X-ray diffraction confirmed the synthesis of copper nanoparticles with an approximate size of 30 nm. Scanning electron microscopy showed copper nanocrystals with a size range of 30–70 nm. The tensile strength showed an approximately 60% rise in the warp direction and an approximately 20% rise in the weft direction for both continuous and exhaust dyeing techniques. The color strength (ratio of absorption co-efficient (K) and scattering coefficient (S); K/S) showed an improvement of 100% and 20% for the exhaust and continuous dyeing techniques, respectively. Both the dyeing techniques showed a rising trend in color fastness to wash and color fastness to rubbing with an increment up to grade 5. The light fastness showed an improvement up to grade 6 for both the techniques. Fastness to rubbing showed an increment from 1 to 5 for both techniques.