Synthetic dyes in textile industry are associated to be toxic and could harm the environment and human health. Following these issues, dyes derived from natural sources have emerged as an important alternative to synthetic dyes. Therefore, this study aimed at production of natural dye extract from mangosteen peel using distilled water. The content of the dye extract was manipulated with and without addition of copper sulphate mordant using simultaneous mordanting method where the presence of the mordant gave various hues on cotton and silk fabrics. The dye extract produced was aimed to be tested for toxicity test and colour fastness test to wash and light exposure. Toxicity of the dye extracts with and without mordant was investigated by using Brine Shrimps Lethality Assay (BSLA). 7 different concentrations of the dye extracts was used for toxicity test containing 10 matured brine shrimps; 15.625, 31.25, 62.5, 125, 250, 500 and 1000 µg/mL, for triplicate. The dye extracts with and without mordant were found to be non-toxic with the LC50 value of the extracts were more than 1000 µg/mL, according to Meyer‟s toxicity index. The resulting wash and light fastness of the fabrics were moderate to good and the mordanting did not result in any significant improvement in fastness properties compared to dye extract without mordant. The indication of accepted fastness properties were according to the ISO 105-C01 and ISO 105-B02 for wash fastness and light fastness, respectively. Based on the studies on toxicity and fastness properties, it was inferred that natural dye from mangosteen peel has good potential to be commercialized in textile industry.