The temperature-dependent kinetics for the reaction between hydrogen peroxide and chloramine water disinfectants (NH2Cl, NHCl2, and NCl3) have been determined using stopped flow-UV/Vis spectrophotometry. Rate constants for the mono- and dichloramine–peroxide reaction were on the order of 10−2 M−1 s−1 and 10−5 M−1 s−1, respectively. The reaction of trichloramine with peroxide was negligibly slow compared to its thermal and photolytically-induced decomposition. Arrhenius expressions of ln(kH2O2–NH2Cl) = (17.3 ± 1.5)–(51500 ± 3700)/RT and ln(kH2O2–NHCl2) = (18.2 ± 1.9)–(75800 ± 5100)/RT were obtained for the mono- and dichloramine peroxide reaction over the temperature ranges 11.4–37.9 and 35.0–55.0 °C, respectively. Both monochloramine and hydrogen peroxide were first-order in the rate-limiting kinetic step and concomitant measurements made using a chloride ion selective electrode showed that the chloride was produced quantitatively. These data will aid water utilities in predicting chloramine concentrations (and thus disinfection potential) throughout the water distribution system.