A threshold collision-induced dissociation (CID) study is performed on dichlorobenzene cation dissociation of both the ortho and para isomers. Ab initio calculations are performed on the system to investigate the details of the potential energy surface with respect to Cl atom loss and to provide the molecular parameters necessary for CID cross section modeling. The effects of kinetic shifts on the CID threshold determinations are investigated using a model that incorporates statistical unimolecular decay theory. The model is tested using unimolecular dissociation rate constants as a function of energy provided by earlier photoelectron-photoion-coincidence (PEPICO) experiments. The different possible sets of parameters involved in the CID model, their effect on the dissociation rates, and their effect on the final CID threshold determination are discussed. A tight transition state is observed to reproduce the experimental dissociation rates better than a phase-space limit loose transition state, a result attributed to a potential energy surface that is much more attractive than a simple ion-induced dipole potential. The dissociation thresholds derived from CID data are in reasonable agreement with the ones derived from fitting the PEPICO rates when similar transition state assumptions are used. A final analysis of the CID data yields 0 K dissociation energies for the Cl atom loss from dichlorobenzene of 3.22+/-0.17 eV for the ortho isomer and 3.32+/-0.18 eV for the para isomer. In the present study we support a mechanism that the dissociations of the two isomers proceed through a direct bond cleavage, rather than through isomerization to a common intermediate.