The investigations of the surface physicochemical and biological properties of polylactic acid modified by silver, argon and carbon ion implantation to doses of 1 × 1014, 1 × 1015 and 1 × 1016 ion/cm2 and energies of 20 keV (for C+ and Ar+) and 40 keV (for Ag2+) are described. X-ray photoelectron spectroscopy revealed that chemical bond ratio in polylactic acid is alternated indicating that different chemical processes take place depending on the implanted ion kind. Chemical reactions that occur during ion implantation of polylactic acid are proposed. X-ray diffraction analysis shows the degree of crystallinity decrease for all the ion types that leads to microhardness and elastic modulus decreasing. Silver is established to form metal nanoparticle into subsurface layer of polylactic acid with the average size of 2–3 nm. It was shown by atomic force microscopy that the higher irradiation doses the lower the surface roughness of polylactic acid that results in hydrophilicity improvement. The cytotoxicity investigation on three individual donor macrophages shows that Ag-implanted polylactic acid has no negative impact on the immune system cells and can be very promising material for biomedical application. •PLA chemical bond ratio is alternated after ion implantation.•Chemical reactions that occur during ion implantation of PLA are proposed.•Implanted silver forms 2–3 nm size metal nanoparticle into the subsurface layer of PLA.•Surface roughness of PLA decreases with the dose enhancing•Ag-implanted polylactic acid has no negative impact on the immune system cells.