Peer victimization (PV) is a serious concern for youth and is associated with subsequent suicide ideation in young adulthood. The interpersonal theory of suicide may provide a framework for understanding suicide ideation in this population. Specifically, thwarted belongingness (TB) and perceived burdensomeness (PB) have been significantly associated with suicide ideation among young adults with a history of peer victimization. Additionally, the personality trait of pessimism is associated with elevated suicide ideation. Thus, this study tested the association between self-reported frequency of retrospective relational (i.e., verbal and indirect) PV in primary and secondary school, thwarted interpersonal needs (TB and PB), and current suicide ideation, as well as how these relations may vary based on current pessimism. Participants were 330 undergraduate students. Nonparametric bootstrap moderated mediation procedures were used to test hypotheses. Results indicated significant indirect effects of frequency of retrospective relational PV and suicide ideation through PB and TB. Contrary to predictions, results did not indicate significant moderated mediation; however, the association between PB and suicide ideation was stronger at lower pessimism levels. We also provide supplemental analysis with optimism as the moderator. These findings suggest that clinicians may consider targeting TB, PB, as well as pessimism and optimism among those with a history of relational PV when assessing and intervening on current suicide ideation. Implications, limitations, and future directions are further discussed.