In summary, a multistate energy decomposition analysis (MS-EDA) method is introduced to dissect the energy components in excimer complexes. Ground-state EDA, which has been extensively explored in the past, remains an active area of research. However, the development of methods for analysis of intermolecular interactions in the excited states has lagged partially because it is difficult to introduce well-defined intermediate states at higher energy levels, not to mention that the computation of excited state energies itself is challenging. Akin to an energy decomposition analysis for the ground state, the present MS-EDA provides a clear separation of energy terms that can be variationally optimized for excited-state complexes. MSDFT based on the Lu-Gao theorems provides a straightforward classification of exciton coupling, superexchange resonance and orbital-configuration expansion. Critical to this analysis is to account for state interaction. As demonstrated in the present study, state interaction provides key insights into an understanding of excitonic coupling and super-exchange stabilization. These quantities, directly computed from the basis states of the MAS for MSDFT, rather than a post priori transformation, are of fundamental importance to determining the rates of electron transfer and excited state energy transfer and in applications to designing light-emitting materials. The examples highlight the roles