A cross-sectional descriptive correlation study was performed to investigate the risk of posttraumatic stress disorder (PTSD) among 300 family caregivers of individuals with schizophrenia or bipolar disorder and examine the relationship between perceived social support and risk of PTSD. The Arabic version of the PTSD Checklist for DSM-5 (APCL-5) was used to investigate risk of PTSD; the Arabic version of the Multidimensional Scale of Perceived Social Support was used to measure perceived social support. Mean score of the APCL-5 was 46.1, indicating risk of PTSD among family caregivers. A negative moderate correlation was found between risk of PTSD and perceived social support. The caring process is demanding and highly stressful, putting family caregivers at risk for PTSD. Social support is crucial in decreasing this risk. [Journal of Psychosocial Nursing and Mental Health Services, xx(x), xx-xx.].; Copyright 2019, SLACK Incorporated.