This study examined the experiences of staff members from seven Japanese hospitals who had been treated aggressively by older dementia clients. Altogether, 170 questionnaires were analyzed. In the past year, 75.3% and 63.5% of staff members had experienced physical and verbal aggression, respectively. Working numerous night shifts, working shifts other than 3-shifts, and being allotted assignments with clients who had a lower average level of physical capacity were the factors associated with recurrent client aggression. Those staff members who spent adequate time caring for their clients, who gained client consent before providing care, and who tried to build a trusting relationship with their clients were found to have experienced less aggression. Burnout, which is likely to enhance the risk of the staff mistreatment and neglect of older clients, was found to be higher among those who experienced aggression.