This study aims to investigate the role of amorphous surface layers on the mechanical response of metallic nanoparticles under compression using molecular dynamics simulations. For this purpose, the transferability of three embedded-atom-method (EAM) potentials to model monoatomic Ni glass and amorphous-crystalline structures is examined. Particular attention is paid to the crystallisation rate of the amorphous shell surrounding the crystalline inner structure. Relying on the most appropriate model, the influence of the amorphous layer on the mechanical response of crystalline-amorphous Ni nanoparticles is further investigated. Regardless of its thickness, the amorphous surface layer significantly changes both the effective elastic modulus of the nanoparticle and the flow stress. Besides stress, dislocation nucleation processes as well as the final shape of the compressed particles are influenced by the presence of the amorphous shell. These results bring new insights on the influence of surface state on the mechanics of metallic nano-objects.