Graphene, a two-dimensional material with a high mobility and a tunable conductivity, is uniquely suited for plasmonics. The frequency dispersion of plasmons in bulk graphene has been studied both theoretically and experimentally, but no theoretical models have been reported and tested against experiments for confined plasmon modes in graphene microstructures. In this Rapid Communication, we present measurements as well as analytical and computational models for such confined modes. We show that plasmon modes can be described by an eigenvalue equation. We compare the experiments with the theory for plasmon modes in arrays of graphene strips and demonstrate a good agreement. This comparison also reveals the important role played by interaction among the plasmon modes of neighboring graphene structures. © 2013 American Physical Society.