The coexistence of magnetic order and valence fluctuations is not so common in a Kondo lattice system. Ce2Rh3Sn5 has a peculiar orthorhombic crystal structure in which Ce ions occupy two distinct lattice sites. Analysis of the structural features of Ce2Rh3Sn5, together with results of electronic band structure calculations and thermodynamic and spectroscopic data indicate that at low temperatures only Ce ions from the Ce1 sublattice adopt a stable trivalent electronic configuration and show local magnetic moments that give rise to the magnetic ordering. By contrast, Ce2 ions exhibit a nonmagnetic Kondo-singlet ground state. Furthermore, the valence of Ce2 ions estimated from the Ce LIII-edge XAS spectra varies between +3.18 at 6 K and +3.08 at room temperature. Therefore, determination of magnetic structure by neutron diffraction study on WISH will be very interesting.