Background: Potentially harmful behaviour (PHB) by caregivers is detrimental to the physical and psychological well‐being of care recipients. In Japan, few studies have investigated caregivers’ PHB towards dementia patients. This study examined PHB in family caregivers of dementia patients with behavioural and psychological symptoms of dementia (BPSD) and identified factors related to PHB. Methods: Following primary consultations at an elderly psychiatric patient department, we enrolled 133 pairs of dementia patients and their family caregivers.