The majority of Afghan asylum seekers and refugees come to Austria from Afghanistan, Iran and Pakistan. While those from Afghanistan faced predominantly war-related traumatic events, those from Iran and Pakistan encountered discriminatory experiences related to the host countries. This vulnerable population’s mental health is further strained by different post-migration stressors in Austria. The purpose of the present study was to explore pre-migration environmental differences and association of different sociodemographic and forced-migration related risk factors to mental health outcomes, and the mediation and moderation effects of post-migration stressors. Data were collected from 305 Afghan participants (155 asylum seekers and 150 refugees) that came from Afghanistan, Iran or Pakistan through nonrandom sampling in Austria. Of the 305 participants, 161 (52.8%) had anxiety, 176 (57.7%) depression, 32 (10.5%) ICD-11 PTSD, and 63 (20.7%) ICD-11 CPTSD. In bivariate analyses, being asylum seeker, being divorced, being Pashtun, and higher number of traumata and stressors in pre-migration and post-migration environments were associated with higher prevalence of mental health problems. Pre-migration traumata and post-migration stressors significantly predicted all mental health outcomes in multiple linear regression analyses. Post-migration stressors significantly meditated and moderated the association between pre-migration traumata and mental health symptoms. The findings support pre-migration traumata’s effects and aggravating role of post-migration stressors in mental health of Afghan asylum seekers and refugees in Austria. Our findings imply the importance of implementing proactive and culturally relevant psychosocial interventions that emphasize prevention of post-migration stressors or mitigating their effects on the mental health.