Wheat straw has been hydrolyzed in two different conditions, namely subcritical water and 100 degrees C boiled water, and the hydrolysates obtained are used to dye wool yarns. The wool samples are pretreated with three types of mordants before dyeing with wheat straw hydrolysates. Irrespective of the metal types used in pretreatment process, subcritical water hydrolysate always results in same color in dyeing process. However, three colors are obtained for each mordant when 100 degrees C boiled water is used as a dyeing reagent. The effect of the total phenolic contents of the hydrolysates on color development has also been evaluated. The total phenolic and sugar contents of subcritical water hydrolysate are found higher and the dyeing performance of this hydrolysate is better than the 100 degrees C boiled water hydrolysate. Light and wash fastness of dyed wools are also assessed. Light and wash fastness tests result in 3-4 and 4-5 rating respectively.