This paper deals with the modeling of devices based on magnetoelectric composite materials. These heterogeneous structures are made of ferromagnetic and ferroelectric materials, the mechanical coupling of which allows obtaining magneto-electric effects exceeding by several orders of magnitude the response of single-phase components. A coupling of the Finite Element Method (FEM) and the Boundary Element Method (BEM) is used to model the behavior of magnetic effects, while classical FEM formulations are used for the electrical and mechanical problems. This coupling of numerical methods allows to avoid considering a free space domain around the active domain, and thus to use a single mesh for the magnetic, mechanical and electrical problems. This results in a consequent reduction of the number of unknowns, which is accompanied by shorter computation times compared to a pure FEM approach. The global algebraic system is solved by a block Gauss-Seidel type solver, which allows a good convergence of the multiphysics.