The nucleation, surface growth and roughening of cobalt electrodeposits on a polycrystalline copper and on amorphous graphite substrates have been studied using electrochemical techniques (voltammetry and chrono-amperometry) and surface imaging by Atomic Force Microscopy (AFM). The influence of the substrate nature and surface preparation on the nucleation and growth mode of Co was investigated as a function of deposition potential and Co thickness. The chrono-amperometry analysis of Co deposits on Cu reveals that the nucleation process agrees with the progressive Armstrong model. Graphite substrate leads to a nucleation process described by the instantaneous Scharifker-Hills model. The morphology and topography aspects examined by AFM denote that the roughness exponent a varies with the film deposition time t while a constant value of the growth exponent b is observed with the two substrates. Cu leads to unstable interfaces characterised by an effective roughness a eff (Co) Cu increasing from 0.30 to 0.8 and b(Co) Cu ΒΌ 0.68 7 0.09 for 10 ot o 1000 s. Graphite gives rise to 0.77Z aZ0.66 and bΒΌ0.1270.03 for 10 o t o250 s corresponding to a stable interface growth whose dynamics is similar to that of the linear molecular beam epitaxy mode bearing a nonconservative noise.