Use of metal salts mordants in naturally dyed textile products make them not fully environmental friendly. We have investigated mango bark extract possibility of being used as a mordant. The natural dye used was extracted from bitter leaves and pre or post mordanted with mango bark extract, the amount of dye in the sample after dyeing and after washing was tested using CIELAB equipment, UV-Vis absorption spectroscopy and wash fastness test. Comparing the mango bark mordanted sample with control samples which included; un-mordanted sample and samples mordanted with copper II sulphate, significant mordanting effect was confirmed which was even better than the conventional mordant used. Further investigation revealed that post mordanting with mango extract gives better wash fastness performance than pre-mordanting. This study forms an important basis on which many more natural materials can be developed to be used as mordants when dyeing not only cotton but other textile products made from other fibers.