Background: Social support is an important feature in understanding posttraumatic stress disorder (PTSD) and its treatment. Non-clinical research has identified distinct profiles of culturally appropriate social support. Despite this, little research has examined cultural influences on social support in the context of PTSD.Objective: This study examined cultural differences in the associations between social support and symptoms of PTSD.Method: The study employed a cross-sectional design. Australian (n = 91) and Malaysian (n = 91) trauma survivors completed an online survey assessing PTSD symptomatology and social support (explicit and implicit social support, perceived helpfulness of support provider, attitudes towards professional help-seeking). A quasi-experimental paradigm assessed the influence of mutual (i.e. the sharing of support between relationship partners) and non-mutual support (i.e. where one person constantly receives support, while the other person constantly provides support) on negative emotion and subjective distress.Results: First, explicit social support was negatively associated with PTSD symptoms for the Australian group but not the Malaysian group. Second, perceived helpfulness of support from family was negatively associated with PTSD symptoms for the Malaysian group but not the Australian group. Third, the Malaysian group reported significantly greater distress for non-mutual support and significantly fewer negative emotions and distress for mutual support than the Australian group. Fourth, the Malaysian group reported that they were significantly more open to acknowledging psychological problems and the possibility of seeking professional help for these problems than the Australian group.Conclusions: As the PTSD social support literature continues to evolve, it is essential that cultural influences are considered given the important theoretical and clinical implications.