Rate coefficients for the gas-phase reactions of Cl atoms with three isomers of dimethylbenzaldehyde (DMBs) have been determined using the relative rate method. Relative rate measurements were performed in a Teflon reaction chamber at 298 ± 3 K and atmospheric pressure. The rate constants obtained (10−11 cm3 molecule−1 s−1) were, respectively, 8.8 ± 1.7, 9.5 ± 1.4 and 9.6 ± 1.6 for 2,4-DMB, 2,5-DMB and 3,5-DMB. This work provides the first kinetic determination of the gas-phase reactions of Cl atoms with DMBs. Our results are compared with the OH reaction with the same DMBs and discussed in terms of structure-reactivity relationship and the atmospheric impact of DMBs.