Nanocrystalline 3μm thick Cu1-xNix (0.45 <x< 0,87) films are electrodeposited galvanostaticaly onto Cu/Ti/Si (100J substrates, from a citrate- and sulphate-based bath containing sodium lauryl sulphate and saccharine as additives. The films exhibit large values of reduced Young's modulus (173<E,<<192CPa) and hardness (6.4<H<8.2GPa), both of which can be tailored bv varying the alloy, composition. The outstanding mechanical proper, of, these metallic films can be ascribed to their nanocrystalline nature-as evidenced by X-ray diffraction, transmission electron microscopy, and atomic force microscopy-along with the occurrence of stacking faults and the concomitant formation of intragranular nanotwins during film growth. Due to their nanocrystalline character, these films also show very low surface roughness (root mean square deviation of around 2nm). Furthermore, tunable magnetic properties, including a transition from paramagnetic to ferromagnetic behavior, are observed when the Ni percentage is increased. This combination of properties, together with the simplicity of the fabrication method, makes this system attractive for widespread technological applications, including hard metallic coatings or magnetic micro/nano-electromechanical devices. © 2010 WILEY-VCH Verlag GmbH & Co. KCaA.