Reaction of AgBr with TabHPF(6) (TabH = 4-(trimethylammonio)benzenethiol) readily produces a unique one-dimensional coordination polymer [(TabH)(AgBr2)](n) ( 1), consisting of anionic chains [AgBr2](n)(n-) with hydrogen bonds to TabH(+) cations. By examining its electrical resistance and stability upon exposure to ammonia and seven common organic amines in water under ambient conditions, compound 1 is found to exhibit good stability and reproducibly high sensitivity toward these analytes at low concentrations. Especially, it can selectively detect NH3 in water with the detection limit as low as 0.05 ppm. This chemiresistive sensing system has the potential for highly efficient monitoring of ammonia and amines responsible for water pollution, eutrophication, food contamination, and industrial hazards.