New triazole-acetate functionalized gold nanoparticles (TTA-AuNPs) for sensitive and selective colorimetric detection of Pb2+ were developed. Aggregation of TTA-AuNPs was induced immediately in the presence of Pb2+, yielding a color change from wine-red to purple. This Pb 2+-induced aggregation of TTA-AuNPs was monitored by the bare eye and UV-vis spectroscopy with a detection limit of 16.7 nM. TTA-AuNPs showed excellent selectivity toward Pb2+compared to other metal ions through the interaction between the carboxyl group and triazole structure of TTA and Pb2+. The best detection of Pb2+ was achieved in a pH range from 5 to 10. Furthermore, TTA-AuNPs were applied to detect Pb 2+ in lake water with low interference.