Ion implantation of polyethylene terephthalate (PET) and polystyrene (PS) with various high energy metallic ions at 70 kV and a dose of 3 × 1016 ions/cm2 has been made. Measurements of the mechanical properties of the polymers before and after implantation have been made with an ultra microindentation system using both pointed and a small (2 μm) radius spherical-tipped indenter. The surface regions were also investigated by atomic force microscopy (AFM) and Rutherford backscattering (RBS). Significant differences have been observed between the Ti–B dual-implanted surfaces and those of the Au and W implanted surfaces. For both the PET and PS, the resistance to indenter penetration at very low loads was much greater for the Ti–B dual-implanted surfaces. The estimated maximum hardness and modulus of the implanted materials were 0.3 and 8 GPa for the PET material and 1.4 and 16 GPa for the PS material. The results obtained with the spherical indenter show a gradual decline in effective modulus of the surface with penetration depth, whereas the hardness or contact pressure goes through a maximum before declining asymptotically to the bulk values. The values of hardness estimated for the spherical-tipped indenter are somewhat more conservative than the optimistic estimates with the Berkovich indenter. The improved increase in hardness for the Ti–B dual-implanted PET material scales with the RBS measured increased depth of implantation.