We present a near-infrared spectroscopy (NIRS) approach for the optical characterization of two-layered tissuemimicking phantoms. For the data acquisition, we employed a multi-distance frequency-domain system. For the data analysis, we implemented an inversion routine based on a two-layered solution of the frequency-domain diffusion equation as the forward model. Measured quantities were the absorption and reduced scattering coefficients of the first layer (μa1, μ’s1) and the second layer (μa2, μ’s2), and the thickness of the first layer (L). We report measurements on three two-layered liquid phantoms featuring absorption coefficients in the range 0.009-0.017 mm-1, reduced scattering coefficients in the range 0.69-0.92 mm-1, and first layer thickness in the range 8-15 mm. Our method yielded measured values of the optical coefficients and first layer thickness (μa1, μ’s1, μa2, μ’s2, and L) that are within 10% of the true values (optical properties measured in the infinite geometry; and the true first layer thickness). These are promising results toward exploring the potential of this two-layered medium approach in the human head, where the two layers would represent extracerebral and cerebral tissue, respectively.