Conventional pretreatment and dyeing processes of viscose fabric are mainly conducted in two baths with substantial amounts of water and auxiliaries. These processes comprise one bath of two–stages for enzymatic de-sizing and alkaline treatment adopted using sodium carbonate with peroxide bleaching formulations and a second bath for the dyeing process. In this study, a regular viscose woven fabric was initially pretreated with a commercial desizing enzyme and subsequently dyed with different reactive dyes in the same exhaust bath process. The effect of one-bath enzymatic pretreatment and reactive dyeing was investigated and optimized, employing enzyme and mono- and/or bifunctional reactive dyes at various concentrations.The results showed that the one-bath pretreatment and dyeing process could be performed successfully, exhibiting remarkable colour strength and excellent performance equal to that with the conventional pretreatment and dyeing method. Both the pretreated fabrics via the bio-method and the conventional one exhibited approximately equal efficiency in terms of improved dyeing and fastness properties. The bifunctional reactive dyes, RR 195 and RBl 5, exhibited higher degrees of dye exhaustion and total fixation yield than those of the monofunctional reactive dyes, RR 180 and RR 31. Although the shorter the one-bath enzymatic pretreatment and dyeing process, all the reactive dyeings using this Bio-method showed comparable CIE L*b*a* and colour difference values E to the conventionally dyed sample using Conv-method, particularly in the case of bifunctional dyes.