Surface acoustic waves have been used successfully in the present work to study the mechanical properties of ion‐exchanged glass surfaces. The surface wave velocity was measured as a function of frequency on an alkali‐aluminosilicate glass before and after sodium for lithium ion exchange. The exchange was carried out at temperatures both above and below the transformation range of the glass and for various treatment times. The surface wave dispersion is explained in terms of depth‐dependent changes in the density and modulus resulting from the concentration gradient caused by the ion exchange. An independent measurement of the density change has allowed a quantitative measurement of shear modulus change in the ion‐exchanged layer. The experimentally determined dispersion curve agrees well with theoretical calculations at frequencies for which the latter are available. The presence of surface stresses has been detected by means of these measurements which has allowed a determination of their time dependence.