This study focuses on issues of elder abuse in residential settings. Violation of ethical principles is shown in the results of this quantitative study aimed at defining the extent, nature and causes of such abuse by employees' unethical conduct towards clients in senior homes (i.e. residential nursing homes) in the Moravian-Silesian region of the Czech Republic. The research sample comprised 454 employees and 488 clients from 12 residential homes for older people. The data were collected from interviews with clients, who also received a questionnaire concerning their satisfaction with the institution. Two questionnaires were administered to the employees, one based on a pilot qualitative study and a second to investigate burnout. Outcomes were assessed according to the extent and form of elder abuse, the causes of elder abuse and the violation of basic ethical principles. The responses, in particular those of employees, revealed both psychological and physical abuse of older clients, and thus violation of two basic principles: respect for the person and non-maleficence. The group at risk of elder abuse comprised aggressive and dissatisfied clients, as well as those with mental problems and dementia. The employees most at risk of being abusers were those who had been employed in institutional care for more than five years, had inadequate knowledge about social services and suffered from burnout. The prevention of elder abuse is recommended to be through education focused on ethical principles, increasing employees' satisfaction by promoting a friendly and safe organizational culture, and providing adequate working conditions.