In this work, adsorption of triclosan (TCS) on nylon 66 membrane is explored to develop a preconcentration and sensing platform. Nylon 66 membrane exhibits superior sorption ability even for trace amounts of TCS (10 μg/L). Investigating the surface adsorption chemistry by XPS analysis revealed the formation of a hydrogen bond between the hydroxyl group of TCS and the amide group of nylon 66. In the absence of TCS, the amphiprotic water molecule forms a multilayer OH group on the membrane surface. However, TCS showed preferential adsorption on the membrane-replacing water molecule due to its higher hydrophobic partition coefficient. We validated the effective preconcentration of TCS on the membrane using LC-MS analysis. Performing colorimetry directly on the TCS-enriched membrane surface showed a visible color change for concentrations as low as 10 μg/L. The relative blue intensity was found to vary linearly over a concentration range of 10-100 μg/L, and we achieved a detection limit of 7 μg/L for a 5 mL sample. This method utilizes easy-to-use resources which drastically reduce the cost and complexity of analysis.