Contact angles of glycerol and diiodometane were measured on glass surface covered by different amounts of humic acids, extracted from a sandy forest soil. The surface coverages with humic acids, surface free energy components and wetabilities of the obtained mixed surfaces were calculated from contact angle values. The dispersion component of the surface free energy increased and the nondispersion one decreased tending to the values for pure humic acids, what was connected with surface coverage increase. The wetability coefficient decreased with humic acids content increase showing hydrophobic action of humic acids.