Diffusion of alkaline-earth ions in mixed cation glasses of the composition xA2O•(3-x)MO•4SiO2 (x = 0.0, 0.1, 0.3, 0.4 and 1.0; A = Na, K; M = Ca, Ba) was investigated by means of the radiotracer diffusion technique below the respective glass transition temperatures. The mobility of alkaline-earth ions increases with the alkali content in all analyzed glass systems with no decrease in the diffusion activation energy, but a raise in the pre-exponential factor. A distinct dependency of the activation energy of the alkaline-earth ions on the type and content of the alkali ions in the glass is observed. Additional experiments with thin glass films derived by the sol-gel technique reveal an analogous diffusion behaviour. This demonstrates that the dynamic of alkaline-earth ions in mixed cation glasses does not depend on the way of glass preparation.