The total quenching rate of NCl(a(1)Delta) metastables by ground-state I(P-2(3/2)) atoms over the temperature range 297-473 K has been studied in a flow reactor. The room-temperature rate coefficient is (2.1 +/- 0.4) x 10(-11) cm(3)/(molecule s). In this temperature range, the temperature dependence for the total quenching rate is described by an Arrhenius expression of k(T) = 1.1 x 10(-10) exp(-519 +/- 143 K/T) cm(3)/(molecule s). The rate coefficient for the energy transfer of NCl(a(1)Delta) to I*(P-2(1/2)) at 300 K is (1.5 +/-0.7) x 10(-11) cm(3)/(molecule s), which is in good agreement with a previous measurement. The magnitude of the energy transfer rate implies a large fraction of the I(P-2(3/2)) is converted to I*(P-2(1/2)), and the NCl(a(1)Delta) + I(P-2(3/2)) reaction is an efficient source of I*(P-2(1/2)). Under the current experimental conditions, a simple kinetic model that simulated the experimental time histories of NF(a(1)Delta) and NCl(a(1)Delta) infers the Cl + N-3 rate coefficient of (1.6 +/- 0.4) x 10(-11) cm(3)/(molecules s) and is slower than previously measured.