The effects of alkali (aqueous NaOH and KOH solutions) pre-treatment on dye exhaustion, color values, color fastness, tensile and surface properties of lyocell yarns were investigated. Dye exhaustion and color yield of lyocell yarns increased by increasing alkali concentrations. The lyocell yarns showed weight loss due to the decrease in carboxyl groups during alkali pre-treatment. The tensile strengths of lyocell yarns decreased with the increase of alkali concentrations because of the decrement of yarn diameter by weight loss the open twist spirals, and the increased volume of lyocell yarns after alkali pre-treatment. The washing and perspiration fastness results of untreated lyocell yarns were better than alkali pre-treated lyocell yarns, while the light fastness results of untreated and alkali pre-treated samples were similar.