The current study examined the 3-week prospective associations between cyber-victimization and both depressive symptoms and rumination. In addition, a mediation model was tested, wherein rumination mediated the association between cyber-victimization and depressive symptoms. Participants (N = 565 college-age young adults) completed online surveys at two time points 3 weeks apart. Results indicated that cyber-victimization was associated with increases in both depressive symptoms and rumination over time. Furthermore, results of the path analysis indicated that cyber-victimization was associated with increases in rumination over time, which were then associated with greater depressive symptoms, providing support for the proposed mediation effect for women, but not men. Findings extend previous correlational findings by demonstrating that cyber-victimization is associated with increases in symptomatology over time. Findings also suggest that the negative consequences of cyber-victimization extend beyond mental health problems to maladaptive emotion regulation. In fact, rumination may be a mechanism through which cyber-victimization influences mental health problems, at least for women. Mental health professionals are encouraged to assess cyber-victimization as part of standard victimization assessments and to consider targeting maladaptive emotion regulation in addition to mental health problems in clients who have experienced cyber-victimization.