Objective: Evidence regarding post traumatic growth (PTG) as a predictor of future reductions in distress has been inconclusive. The purpose of this study was to examine this relationship in a multiple-observation prospective study, to provide a more rigorous test of prediction over time. This longitudinal study extended previous work by taking into account perceptions of vulnerability and explored the buffering role of PTG on the links between vulnerability and psychological distress. We also explored whether individual differences in demographic and medical characteristics moderate the relationship of interests. Method: Participants were 312 Taiwanese women (Mage = 46.7 years) who underwent surgery for breast cancer. Measures of PTG, perceived vulnerability, and distress were assessed at Day 1 and 3, 6, 12, and 24 months after surgery. Hierarchical linear modeling was used to investigate whether PTG and vulnerability and their interaction predicted distress over time. Results: A significant direct effect of PTG on distress was found: higher PTG was followed by lower distress. Analysis also yielded a significant buffering effect of PTG on vulnerability leading to distress. However, this effect was moderated by type of surgery. The buffering effect of PTG occurred only among women having mastectomy. Conclusions: We conclude that PTG tends to lead to less psychological distress overall but particularly so in a high impact context.