A model for homogenization of the elastic-plastic properties of isotropic interpenetrating-phase composites (IPCs), which combines the continuum strain models of heterogeneous solid and porous materials, is suggested. A distinctive feature of the model consists in calculating the concentration ratios of average Hill strains in terms of the effective volumes of averaged strains. These strains are determined from the solution of boundary value problems on the elastic or plastic deformation of a simplified representative cell of two-phase IPCs considering the porosity of the material. Calculation results are compared with experimental data. Judging from the set of results obtained, the new model describes the elastic and plastic properties of IPCs more accurately than the well-known analytical ones.