We have investigated the influence of a spatially non-uniform anisotropy fluctuation on the magnetization reversal dynamics in ferromagnetic thin films. A Monte Carlo algorithm has been adopted to characterize a thermally activated reversal process during magnetization reversal within the context of a micromagnetic theory. Interestingly, the results revealed that a non-uniform anisotropy fluctuation has a crucial effect on the magnetization reversal dynamics: the magnetization reversal dynamics changes from wall-motion dominant to nucleation dominant with a small change in the spatial anisotropy fluctuation.