A study of the magnetic aftereffect in co-precipitated cobalt ferrite is presented.Measurements of the magnetic viscosity S were performed at room temperature along the demagnetization curve for different applied fields Hap over a wide range of fields (0 kOe<Hap<- 7 kOe).The interrelation function n ¼ ðMrev/ðMirr)Hi between the DCD reversible Mrev and irreversible Mirr magnetization components was determined as well. The experimental results for Sn (Hi) where Hi is the internal field, showed a broad distribution with a maximum at Hi = 2.7 kOe. However, the irreversible susceptibility Xirr displays a maximum at Hc = 0.75 kOe, the coercivity of the material. The experimental behavior of n and the non-proportionality between Sn and Xiirr suggest that the magnetic viscosity in this material is principally supplied by events of nucleation of inverse domains and the depinning of domain walls. When the main mechanism of reversal magnetization changes to rotation of magnetic moments for all the grains, the magnetic viscosity decreases.