Dynamic scaling analysis was applied to the investigation of the roughening kinetics of Co-Ni and Co-Ni-P films electrodeposited from acidic (pH 3) chloride solutions. Co-Ni films exhibit uninhibited growth with the formation of well-defined crystal facets, while Co-Ni-P films exhibit a granular microstructure with a much smaller apparent grain size. Correspondingly, the rate at which Co-Ni-P films roughen is much slower than that of the Co-Ni films. This is ascribed to autocatalytic processes during Co-Ni-P deposition occurring in parallel with electrochemical processes, inducing growth inhibition due to the ongoing nucleation, incorporation of phosphorus, and enhanced hydrogen evolution. The slow roughening of Co-Ni-P films is advantageous for microfabrication processes involving the formation of thick magnetic films and microstructures.