The title reaction was studied using two different experimental techniques: laser flash photolysis with resonance fluorescence detection of Cl atoms and continuous photolysis with FTIR detection of end products. Over the temperature range 206-432 K the rate constant for reaction of Cl atoms with CH ₂ICl is given (to within ±15%) by the Arrhenius expression k ₁ = 4.4 × 10 ^-11 exp(195/T) cm ³ molecule ^-1 s ^-1, which gives k ₁ = 8.5 × 10 ^-11 cm ³ molecule ^-1 s ^-1 at 298 K. Variation of the total pressure of N ₂ diluent over the range 5-700 Torr at 295 K had no discernible (<10%) effect on the rate of reaction. At 295 K in 100-700 Torr of N ₂ the reaction proceeds via iodine transfer to give CH ₂Cl radicals. As part of this work the rate constant k(CH ₂Cl+O ₂+M) was measured at 295 K in the presence of 1-800 Torr of N ₂ diluent. The results were well described by the Troe expression with a broadening factor F _c of 0.6 and limiting low- and high-pressure rate constants of k ₀ = (1.8 ± 0.1) × 10 ^-30 cm ⁶ molecule ^-2 s ^-1 and k _∞ = (3.3 ± 0.3) × 10 ^-12 cm ³ molecule ^-1 s ^-1. The results are discussed with respect to the available literature for reactions of Cl atoms with halogenated organic compounds and the potential role of the title reaction in atmospheric chemistry.