Redundant nickel is harmful to human health and can result in skin diseases, allergies, or cancer. Although many probes based on noble metal nanoparticles have been established for rapid heavy metal ion detection by the naked eye or ultraviolet-visible (UV-vis) spectroscopy, few noble metal nanomaterials have been developed for Ni2+ detection. In this study, we propose novel triangular silver nanoprisms (AgNPRs) stabilized with glutathione (GSH) for rapid colorimetric detection of Ni2+ based on a sensing mechanism of anti-etching, which has been affirmed by Raman spectra, UV-vis spectra, transmission electron microscopy, and dynamic light scattering. At the optimal experimental parameters, our GSH-AgNPR-based Ni2+ probe has an excellent selectivity compared with those of 26 other ions because Ni2+ can inhibit the AgNPR etching by iodide ion (11 (i.e., anti-etching) while other ions cannot. The limit of detection (LOD) of our Ni2+ probe is 50 nM via the naked eye and 5 nM via UV-vis spectroscopy. They are both negligible compared with the permissible limit of Ni2+ in drinking water (0.34 mu M) prescribed by the World Health Organization. In particular, the latter is far lower than the LOD values of other reported Ni2+ probes based on noble metal nanomaterials. A satisfying linear relationship reinforces that our probe can be utilized for the quantitative analysis of Ni2+. The detection of real water samples indicates that our probe could be used for rapid Ni2+ colorimetric detection with supersensitivity and excellent selectivity in real environmental water samples.