The propagation of a Stoneley wave through an inclusion near a liquid/solid interface is investigated on the basis of mode theory [Briers et al., J. Acoust. Soc. Am.95, 1953–1966, 1967–1976 (1994)]. An expression for the phase and amplitude changes of the Stoneley wave is derived and analyzed in the case of a thin (kd≪1) and of a thick (kd≫1) inclusion of arbitrary length (kdis the multiplication of the liquid wave number with the thickness of the inclusion).