Strengthening by twin boundaries at nanoscale and gradient surface nanocrystallization are two important strengthening approaches recently drawing considerable attention in the field of metallic material research. In the present work, a novel nanostructure, i.e., gradient nanoscale twin boundaries, is proposed. To reveal their unique deformation mechanism, uniaxial tension simulations of gradient nanotwinned copper are investigated by molecular dynamics simulations. The results show that partial dislocations govern the deformation of relatively thicker twins while full dislocations control the deformation of relatively thinner twin layers. Nanoindentation processes of gradient nanotwinned copper are also performed, providing insights on the strengthening and hardening effects of nanoscale twin boundaries.