Acid or base compounds in industries as well as acid rain are colorless so that they have difficulty in detecting. In the previous studies, we investigated a nylon chemosensor for detecting acidic liquids. In this study, we attempted to investigate a wool-based textile sensor using bromocresol purple as a pH-indicating dye. Dyeing properties of bromocresol purple on a wool woven fabric were investigated. The pH sensing property was also investigated by dipping the dyed wool fabric in aqueous solution with different pH values. Bromocresol purple in an aqueous solution showed maximum absorption at 432 nm with yellow color at a pH of 2-4, whereas the maximum absorption changed to 589 nm showing violet color at pH 7. Color yields (K/S) of bromocresol purple on wool were highly dependent on the dyebath pH. The wool fabric showed a strong orange color when dyed at pH 2. The color of wool dyed at pH 3-6 was yellowish brown or reddish brown, and the color at pH 7 was grayish blue. The percent exhaustion of bromocresol purple on wool increased as the pH of dyebath decreased, and a high exhaustion value of 98 to 99% could be obtained at pH 2-4. When the yellowish brown sample, dyed at pH 4, was immersed in a solution with a pH range of 4-5, its original color was maintained. Then, the color turned to yelloworange when immersed in a solution of pH 2-3. When immersed in a solution of pH 6, the color of the sample changed into brown. The color was also markedly changed into grayish purple when the sample was dipped in a solution of pH 7-8. The wash fastness of the wool fabric dyed at pH 3-5 was good to very good. The rubbing fastness were excellent, and dry cleaning fastness was very good.