The purpose of this study is to investigate the natural frequencies and mode shapes of beam-columns on the non-homogeneous foundation. The beam model is based on the classical Bernoulli - Euler beam theory. The linear foundation modulus is chosen as the non-homogeneous foundation in this study. The differential equation governing free vibrations of such beam-columns subjected to axial load is derived and solved numerically for calculating the natural frequencies and mode shapes. In numerical examples, five kinds of end constraint are considered, and the lowest four natural frequencies and corresponding mode shapes are obtained as the non-dimensional forms.