Social support may be a protective factor for the mental health of public safety personnel (PSP), who are frequently exposed to potentially psychologically traumatic events and report substantial post-traumatic stress disorder (PTSD) and major depressive disorder (MDD) symptoms. Research examining perceived social support and its association with PTSD and MDD in different PSP categories (e.g. firefighters, paramedics) is limited. To examine differences in perceived social support across PSP and determine whether perceived social support is associated with differences in rates of MDD and PTSD. We asked Canadian PSP, including correctional workers and officers, public safety communications officials, firefighters, paramedics, municipal and provincial police officers, and Royal Canadian Mounted Police (RCMP) officers, to complete an online anonymous survey that assessed socio-demographic information (e.g. occupation, sex, marital status, service years), social supports and symptoms of mental disorders, including PTSD and MDD. Analyses included ANOVA and logistic regression models. Perceived social support differed by PSP occupation. RCMP officers reported lower social support than all other PSP except paramedics. For most PSP categories, PSP who reported greater social support were less likely to screen positive for PTSD (adjusted odds ratios [AORs]: 0.90-0.93). Across all PSP categories, greater perceived social support was associated with a decreased likelihood of screening positive for MDD (AORs: 0.85-0.91). Perceived social support differs across some PSP categories and predicts PTSD and MDD diagnostic status. Studies involving diagnostic clinical interviews, longitudinal designs and social support interventions are needed to replicate and extend our results.