Caregiving has been associated with increased levels of fear and post-traumatic stress symptoms (PTSS) during COVID-19 pandemic. However, there is a lack of studies that analyze when the relationship between fear and PTSS occur, using informal caregiving as a moderator variable. To explore this moderating role, we conducted a cross-sectional online study between November 2020 and January 2021. A total of 503 men and women from the Spanish general population completed the survey. Sociodemographic and Covid-19-related data, fear of COVID-19, PTSS symptoms, and current psychological history were assessed. Prevalence of informal caregiving in the sample was 16.5%. Increased levels of fear and PTSS were found in caregivers compared to non-caregivers. Female gender and high number of COVID-19 related risk factors was also associated with fear and PTSS severity. The moderation analyses showed an interaction effect between caregiving and fear of COVID-19 when predicting PTSS symptoms. Particularly, results showed that informal caregivers reported greater PTSS symptoms, when compared to non-caregivers with same levels of fear of COVID-19. This evidence suggests that being a caregiver could increase the fear's impact on PTSS severity in the context of pandemics. Further studies with larger samples are needed to confirm these findings.