© 2020 Guilford Publications. All rights reserved. Objective: Research driven by terror management theory suggests sociocultural anxiety-buffer systems typically protect against existential anxiety, whereas anxiety buffer disruption theory suggests traumatic experiences may disrupt that process. Method: Following posttraumatic stress (PTS) symptom screening (n = 4097), individuals with low (n = 149) and high (n = 120) PTS engaged in either negative or positive self-evaluations, then reported death anxiety and appraised life's stressors as negative/threatening or positive/challenging. Results: When low PTS participants contemplated their worst (vs. best) selves, they experienced moderately heightened death anxiety yet appraised life's stressors as more positive/challenging than harmful/threatening, reflecting effective existential anxiety buffers. However, high PTS participants reported high death anxiety in both the best-self and worst-self conditions-indicating anxiety buffer disruption-and the worst-self (vs. best self) prompt increased their appraisal of life's stresses as a harmful threat and decreased appraisal as positive/challenging opportunities for growth and well-being. Discussion: Theoretical and clinical implications are discussed.