We introduce a high order interior penalty discontinuous Galerkin scheme for the nu- merical solution of wave propagation in coupled elasto-acoustic media. A displacement formulation is used, which allows for the solution of the acoustic and elastic wave equations within the same framework. Weakly imposing the correct transmission condition is achieved by the derivation of adapted numerical fluxes. This generalization does not weaken the discontinuous Galerkin method, thus hp-non-conforming meshes are supported. Interior penalty discontinuous Galerkin methods were originally developed for scalar equations. Therefore, we propose an optimized formulation for vectorial equations more suited than the straightforward standard transposition. We prove consis- tency and stability of the proposed schemes. To study the numerical accuracy and convergence, we achieve a classic plane wave analysis. Finally, we show the relevance of our method on numerical experiments.