Objective The present study examines the effects of attachment styles on the grief response and the indirect effect of rumination in parents who lost a child in the Sewol Ferry accident. Methods Bereaved parents (n=81) completed self-report questionnaires evaluating their attachment style (Experience in Close Relationship-Short form), traumatic loss related rumination (Event-Related Rumination Inventory), degree of complicated grief (Inventory of Complicated Grief), and post-traumatic growth (Post-Traumatic Growth Inventory). Data were analyzed using correlation analysis, structural equation modeling, and bootstrapping. Results The indirect effect of event-related intrusive rumination was significant in the relationship between attachment avoidance and complicated grief. The path from attachment avoidance to post-traumatic growth via deliberate rumination was not significant. With respect toattachment anxiety and post-traumatic growth, the indirect effect of deliberate rumination was significant. But the indirect effect of intrusive rumination was not significant in the relationships among attachment anxiety, complicated grief, and post-traumatic growth. Conclusion Individuals with attachment anxiety could obtain post-traumatic growth via deliberate rumination. By contrast, attachment avoidance was associated with the risk of maladaptive grief. Grief interventions should account for individual differences in attachment styles through interventions that manage intrusive rumination and strengthen deliberate rumination.