OBJECTIVE: Failing to account for temporal dynamics can hinder our understanding of suicidal ideation and the potential mechanisms underlying increased risk for suicide death and suicide attempts associated with posttraumatic stress disorder (PTSD). To address these limitations, this study used an analytic approach based on Dynamical Systems Theory to describe temporal patterns associated with multiple dimensions of suicidal ideation in a treatment-seeking sample of military personnel diagnosed with PTSD. METHOD: We performed a secondary analysis of archived data from 742 active-duty military personnel (90% male, 57% white, mean age = 33 ± 7.4 years) enrolled in three clinical trials to examine the dimensional measurement properties of the first 5 items of the Scale for Suicidal Ideation (SSI). RESULTS: Findings indicated two change dynamics for suicidal ideation: homeostatic (i.e., the tendency for suicidal ideation to return to a stable point) and cyclical (i.e., the tendency for suicidal ideation to switch back and forth between higher and lower values). Cycling was the dominant dynamic and was related to variables other from suicidal ideation. CONCLUSION: The cyclic nature of suicidal ideation suggests that assessment timing and context could influence observed associations with other variables. Analytic approaches and clinical methods that do not account for the temporal dynamics of suicide risk could miss these properties, thereby hindering efforts to identify mechanisms underlying the relationship between PTSD and suicidal thoughts and behaviors and limiting opportunities for proactive and timely intervention. (PsycInfo Database Record (c) 2021 APA, all rights reserved).