The present work involves the dyeing of pure wool fabrics with a natural dye extracted fromthe violet flowers of Calotropis procerea plant Erichrome black T as a pre-mordant. The effect of dyeing time, temperature and pH value of the dye bath, using, on the reflectance spectra of the fabrics was followed using spectrophotometer tool and CIE tristimulus values. The color yields of the dye on thewool fabricswere found to be highly dependent on these different dyeing conditions. The beneficial effects of varying conditions of dyeing on the color parameters L, a, b, h, c and the change in color difference (ïE) were also investigated. Light and washing fastness were carried according to ISO standard recommendations to evaluate the amount of fading in terms of color difference to deduce the influence of dye-fiber bonding. The Fourier transform infrared (FTIR) spectra of dyed wool fabrics were followed at each dyeing conditions. The results indicated that, the behavior of the change in the peak intensity values of different functional groups present in the wool fabrics are completely different by changing dyeing conditions. The obtained results indicate that the improvement in dyeing process may be due to the change in the molecular configuration as a result of the variation in the chemical bonds in wool fabrics, the dye and/or the mordant. This means that the increase in the amorphous region of the dyed samples, the oxidation of the cystine linkage on the surface of the wool fabrics, and the formation of free-radicals species encouraged dye penetration and aggregation inside the fiber pores as well as bond formation. The standardization of dyeing and mordanting mechanisms are discussed, as well as the evaluation of the dyeing parameters and fastness properties and reported CIELab data.