We report a breakdown of Barkhausen critical-scaling behavior in NiO/Fe films with increasing domain-wall pinning by means of a Kerr microscope capable of direct domain observation. The time-resolved domain images in the films revealed that the Barkhausen jump size is generally decreased with increasing NiO thickness, showing an enhanced domain-wall pinning effect. Interestingly enough, the power-law scaling behavior of the Barkhausen jump size distribution gradually disappears as pinning of domain walls in the Fe layer is increased. This is ascribed to the fact that the magnetization reversal mechanism is changed from a Barkhausen avalanche dominant mode to domain-wall creep dominant mode. © 2011 American Physical Society.