We consider a linearly elastic composite medium, which consists of a homogeneous matrix containing coated spherical inclusions. The composite is modeled by a four phase pattern consisting of inclusion, interphase, matrix layer, and equivalent homogeneous medium. The overall elastic moduli are obtained using a micromechanical approach based on the Green function techniques and the interfacial operators. The four phase model assumes that all constituents are elastic and perfectly bonded. The model is used to derive the effective elastic properties of representative volume element using classical averaging schemes assuming the isotropy of constituent. Finally, effect of the thickness and stiffness of interphase on the global behavior of real composite materials are examined. Comparisons with experimental results show a good agreement.