The bleaching of modal/AN-g-casein fiber blend using hydrogen peroxide/tetraacetylethylenediamine (H2O2/TAED) activating system was investigated, and the influence of key factors on bleaching was determined. The whiteness index of bleached fabrics was greatly affected by sodium carbonate and H2O2/TAED dosages, and the dyeability of bleached fabrics with acid dyes was greatly dependent on H2O2/TAED dosages and bleaching temperature. Compared with the conventional H2O2 bleach under alkaline conditions, the activated bleach markedly decreased the loss of casein in AN-g-casein fiber due to its acidic conditions, and exhibited the advantages of energy saving and high efficiency. However, the fabrics bleached using the activated process had the poor acidic dyeing properties due to the oxidation of amino groups in AN-g-casein fiber. (c) 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012