This is a theoretical study of the photochemistry of Cl2O based on ab initio potential energy surfaces and trajectory surface-hopping calculations. We calculated quasidiabatic states and couplings for eight singlet states of Cl2O with a multireference perturbation configuration interaction (CI) technique. Analytical representations of the three-dimensional potential energy surfaces and electronic couplings were used for semiclassical simulations of the nonadiabatic dynamics of excited Cl2O up to 5.4 eV. The computational results allow us to relate the photodissociation mechanism to observable quantities such as the anisotropy of the recoil velocity and the translational energy distribution of the fragments.