Posttraumatic growth (PTG) is viewed as a positive psychological change resulting from a struggle with trauma. A number of trauma-related factors have been proven effective in predicting PTG; however, the effects of pretrauma psychological factors on PTG have not been adequately evaluated (e.g., using a prospective design). This prospective study examined the effects of pretrauma psychological factors (e.g., coping styles, prior trauma) on PTG. In total, 810 Taiwanese undergraduate students were recruited for a baseline survey (Time 1), among whom 592 completed a survey 2 months later (Time 2). Data from 110 participants who had experienced trauma between Time1 and Time 2 were used for analysis. Among the pretrauma factors examined at baseline, only rumination and distractive style were positively correlated with PTG. The posttrauma factors based on Calhoun and Tedeschi's model (i.e., core belief challenge, deliberate rumination, and social support) were also positively correlated with PTG. A hierarchical regression analysis showed that pretrauma coping styles had an incremental effect on PTG beyond posttrauma predictors. Deliberate rumination signifciantly mediated the relationship between pretrauma rumination and PTG. These findings highlight the role of pretrauma psychological factors in PTG and present further support for Calhoun and Tedeschi's model of PTG.