This study tested the role of perceived social support as a moderating factor in the mediation of COVID-19-related concerns in the association between continuous traumatic stress (CTS) and depression. The study participants were 499 college students who responded to an anonymous online questionnaire. Measures included the assessment of prior continuous exposure to threats of terrorism, COVID-19-related distress, perceived social support and depressive symptoms. The results demonstrated that COVID-19-related concerns mediated the relationship between continuous exposure to threats of terrorism and depression symptoms, and that perceived social support moderated the association between COVID-19-related concerns and depression. The implications of the study highlight the role of prior exposure to traumatic stress as a risk factor for depression and the role of social support as a protective factor. These results point to the need to develop accessible and non-stigmatic mental health services for populations exposed to other types of continuous traumatic stress.