Valence electronic excitation spectra are calculated for the H2O center dot center dot center dot Cl-2 dimer using state-of-the art ab initio potentials for both the ground and the valence excited states, a basis set calculation of the ground state nuclear wave funtion, and a wave packet analysis to simulate the dynamics on the excited state surface. The peak of the H2O center dot center dot center dot Cl-2 dimer spectrum is blue-shifted by 1250 cm(-1) from that of the free Cl-2 molecule. This is less than the value previously estimated from vertical excitation energies but still significantly more than the blue shift in aqueous solution and clathrate-hydrate solid. Seventy percent of the blue shift is attributed to ground state stabilization, the rest to excited state repulsion. Spin-orbit effects are found to be small for this dimer. Homogeneous broadening is found to be slightly smaller for the dimer than for the free Cl-2. The reflection principle and spectrator model approximations were tested and found to be quite satisfactory. This is promising for an eventual simulation of the condensed phase spectra.