We present a new electronic structure approximation called Tight Binding Configuration Interaction. It uses a tight-binding Mamiltonian to obtain orbitais that are used in a configuration interaction calculation that includes explicit charge interactions. This new method is better capable of predicting energies, ionization potentials, and fragmentation charges than the Wolfsberg-Helmholz Tight-Binding and Many-Body Tight-Binding models reported earlier (Staszewska, G.; Staszewski, P.; Schultz, N. E.; Truhlar, D. Phys. Rev. 6 2005, 71, 045423). The method is illustrated for clusters and nanoparticles containing aluminum.