The dyestuff from onion (Allium cepa L.) was extracted using Soxhlet apparatus with distilled water. Wool and cotton fabrics were pretreated with (urea+ammonia+calcium oxalate ) mixtures, artificial animal urine system (AAUS) before dyeing. The solutions 0.1 M of CuSO4, FeSO4 and AlK(SO4)2.12H2O were used as mordant agents. Pre-mordanting, together mordanting and last mordanting methods were applied at pH =4 and pH= 7 for dyeing of fabrics. According to the fastness results, the best dyeing method was determined as together mordanting method at pH=4 for wool and last mordanting method at pH= 7 for cotton fabric. The results also reveal that the onion containing Quercetin dyestuff shall probably be an important raw material for dyeing process of natural textile fibers