The Perfectionism Social Disconnection Model (PSDM) and the Existential Model of Perfectionism and Depressive Symptoms (EMPDS) are promising models of perfectionism and psychopathology. However, research examining suicide ideation within the PSDM is scarce, and no research has examined suicide ideation as an outcome in the EMPDS. Moreover, tests of the PSDM and EMPDS have been conducted separately and most research has examined the PSDM and EMPDS using cross-sectional or two-wave longitudinal designs, which do not provide a satisfactory test of mediation. In the current study, we addressed these limitations by testing whether perfectionism confers vulnerability to suicide ideation via feelings of mattering and anti-mattering (from the PSDM) and via difficulty accepting the past (from the EMPDS) in a three-wave longitudinal design in two independent samples of undergraduate students and community adults. Participants completed measures on three occasions over 6 weeks. Findings revealed that socially prescribed perfectionism indirectly predicted suicide ideation via difficulty accepting the past in both samples. In addition, in the undergraduate sample only, socially prescribed perfectionism indirectly predicted higher suicide ideation via anti-mattering, and self-oriented perfectionism indirectly predicted higher suicide ideation via mattering. Based on our findings, we advocate for future research to include suicide ideation in the PSDM and EMPDS, to integrate explanatory models, and to examine a mattering-specific EMPDS.