The current study aimed to measure the stress levels of family caregivers of individuals with mental illness and compare their stress levels according to the diagnosis and other sociodemographic characteristics. The sample comprised 310 family caregivers of individuals with mental illness in Jordan. Family caregivers completed a demographic checklist and the Arabic version of the Perceived Stress Scale 10-Item (PSS-10) questionnaire. A significant difference was found in PSS-10 levels among family caregivers according to gender, diagnosis of their family member, and time since diagnosis. Female caregivers reported significantly higher stress levels than male caregivers. Family members of individuals with schizophrenia reported the highest stress levels (p < 0.001). Results also indicated that there was a significant negative correlation between PSS-10 levels of family caregivers and time since diagnosis. Investigating stress levels in family members of individuals with mental illness may be helpful when designing interventions to reduce such stress. [Journal of Psychosocial Nursing and Mental Health Services, 55(6), 30-35.].; Copyright 2017, SLACK Incorporated.