Background: Burnout, especially emotional exhaustion, is common among mental healthcare providers (MHP). It is caused by exposure to prolonged stress related job conditions, such as secondary traumatisation. Social support is a protective factor for developing emotional exhaustion. In addition, higher levels of social support are associated with lower levels of secondary traumatisation. However, it is unclear how social support and secondary traumatisation are related. Social support may be a protective factor for developing secondary traumatisation, as it is for emotional exhaustion. On the other hand, MHP who suffer more from secondary traumatisation might experience less social support, for example because they fear stigmatisation. This study examined whether social support mediates the relationship between secondary traumatisation and emotional exhaustion. Further, it is explored whether the relation between secondary traumatisation and social support is moderated by profession (physicians, psychologists and case managers). Method: In total, 593 MHP participated in this cross-sectional study. Participants completed a questionnaire including demographic characteristics, secondary traumatisation, emotional exhaustion, and social support. Results: It was shown that no MHP experience high levels of secondary traumatisation and relatively few experience high levels of emotional exhaustion, while they do experience much social support. Furthermore, as hypothesized, it was found that the relationship between secondary traumatisation and emotional exhaustion is partially mediated by social support. Finally, no moderation effect of profession was found. Conclusion: These results imply that MHP have access to social support and make use of it, preventing emotional exhaustion.