The trunk and its muscles play an important role in maintaining walking mechanics. Fatigue and weakness of these muscles could affect walking mechanics adversely. The trajectory of the center of pressure (COP) reflects whole body mechanics. The aim of this study was to investigate the effect of trunk muscles fatigue on the trajectory of the COP during walking. Totally, 20 female academic students participated in this study. Participants were asked to walk on the walkway before and after trunk muscles fatigue with self-selected speed. In the midway of the walkway, a footscan pressure mat was mounted. The COP trajectory, relative timing of stance phases and foot progression angle were recorded using footscan in pre- and post-fatigue conditions. After fatigue, the relative time of the initial contact phase increased and the relative time of forefoot contact phase decreased. Trunk muscle fatigue lateralized the COP trajectory in the Forefoot Flat Phase and Forefoot Push-off Phase and decreased foot progression angle. According to the results of the current study, it can be concluded that fatigue and weakness of trunk muscles lead to changes in walking mechanics. These changes could expose people to the risk of injury.