This study presents dyeing behavior aspects with Allium Cepa infusion of 100% wool yarns and 70%wool/ 30% Angora mohair blended yarns. Variants of yarns that were pre-treated according to the classical procedure of scouring were compared with variants of yarns that were subjected to proteolytic enzyme pre-treatment. The pre-mordanting technique with potassium alum was experimented. The influence of pre-treatments on natural dyeing was studied in terms of dyeing intensity, color fastness to washing, artificial light, acid and alkaline perspiration, physical-mechanicaland physical-chemical characteristics. Colour measurements have evidenced an increase of the tinctorial affinity to natural dye of wool fiber subjected to preliminary enzyme treatment followed by pre-mordanting. In the case of wool-Angora mohair blended yarns the tinctorial affinity to natural dye does not improve. Colour fastness to washing, acid and alkaline perspiration is good and very good for all the variants of treatment applied. Pre-mordanting has not positively influenced the colour fastness to light. Preliminary processes applied either in the classical or in the enzyme variant followed by pre-mordanting and dyeing induced a decrease of the breaking strength of 100% wool yarns by approx. 20% in the case of classical treatment and by 16% in the case of enzyme treatment while they do not negatively influence the breaking elongation values. For wool- Angora mohair blended yarns the enzyme treatment was much more aggressive compared to the classical one, leading to much lower values of the breaking strength, compared to the raw witness yarns, the decreases re aching up to 40%.