Research has documented a strong association between perceived social support, posttraumatic stress symptoms (PTSS), and psychological distress (PD) among people exposed to natural disasters. However, the direction of associations between these factors remains unclear. This study examined possible mediational relationships among perceived social support, PTSS, and PD. A three-wave longitudinal design (6 months intervals) was employed in a sample of 341 Chinese university students (M = 21.24, SD = 2.72; 75.7% female) aged 18 to 34 who were directly exposed to a typhoon that occurred in Macao, China, during August 2017. Results indicated that perceived social support at T2 mediated the linkage between PTSS at T1 and PD at T3, and that PTSS at T2 significantly mediated the relationship between PD at T1 and perceived social support at T3. This three-wave longitudinal study highlights the key role of perceived social support on the aggravating effect of acute PTSS on long-term psychological problems, and demonstrates that adverse psychological health outcomes negatively affect the perception of supportive social resources in the context of a natural disaster.