Measurements of charge transfer cross sections for the K+ - Ar system are reported. The measurements are performed at low incident energy (0.25 - 4.30 keV). We compare the experimental results with previous data and a semiempirical calculation. The present results show an overlap with existing measurements and extend down in energy to 0.25 keV. Good agreement in behavior has been found between the semiempirical calculations and the present experimental data.