Nanocrystalline　Ni-Cu　alloys　with　a　Cu　content　of　6,　10,　19,　and　32 wt.%　were　prepared　by　pulse　electrodeposition.　The　microstructure　and　tensile　properties　of　the　nanocrystalline　Ni-Cu　alloys　were　characterized　by　x-ray　diffraction,　transmission　electron　microscopy,　and　tensile　testing.　The　x-ray　diffraction　analysis　indicates　that　the　structure　of　the　nanocrystalline　Ni-Cu　alloys　is　a　face-centered　cubic,　single-phase　solid　solution　with　an　average　grain　size　of　18　to　24　nm,　and　that　the　average　grain　size　decreased　with　increasing　Cu　content.　The　ultimate　tensile　strength　(~1265　to　1640 MPa)　and　elongation　to　failure　(~5.8　to　8.9%)　of　the　Ni-Cu　alloys　increased　with　increasing　Cu　content.　The　increase　in　tensile　strength　results　from　the　solid　solution　and　fine-grain　strengthening.　Elemental　Cu　addition　results　in　a　decrease　in　stacking　fault　energy,　an　increase　in　work　hardening　rate,　a　delay　in　plasticity　instability,　and　consequently,　a　higher　plasticity.　©　2016,　ASM　International.