Inadequate mechanical surface properties limit the service life of ultra-high molecular weight polyethylene (UHMWPE) hip and knee joint components. It is well known that in vivo wear resistance of UHMWPE can be improved by crosslinking, but concomitantly its fatigue strength is reduced. M. del Grosso et al. have shown that irradiation with 33MeV N ion beam at fluences ranging from 5×10¹⁰ to 1×10¹⁴ ions/cm² induces strong chemical modifications in the outer layers of the polymer. Thus it appears that, by means of this irradiation technique, it may be possible to generate suitable surface modifications without affecting the desirable bulk properties of UHMWPE. The motivation of this work was to examine nanoscale mechanical properties of the outer layer region of N beam irradiated UHMWPE using depth-sensing indentation. Reduced elastic modulus and universal hardness were determined applying trapezoidal loading functions with a Berkovich tip by means of the Oliver-Pharr approach. The apparent friction coefficient was evaluated from nanoscratch tests carried out with a 20 µm conospherical tip. The irradiated samples exhibited better performance than unirradiated ones, ie. higher elastic modulus and hardness, and lower friction coefficient, suggesting a better wear resistance. The magnitude of these properties was shown to be dependent on fluence under the irradiation conditions used. UHMWPE irradiated with 1×10¹² ions/cm² exhibited a four-fold increase of hardness and elastic modulus and at one point five-fold decrease of friction coefficient.