Most research and theory on identity integration focuses on adolescents and young adults under age 30, and relatively little is known about how identity adjusts to major life events later in life. The purpose of the present study was to operationalize and investigate identity disruption, or a loss of temporal identity integration following a disruptive life event, within the developmental context of established adulthood and midlife. We used a mixed-methods approach to examine identity disruption among 244 Afghanistan and Iraq war veterans with reintegration difficulty who participated in an expressive writing intervention. Participants completed measures of social support, posttraumatic stress disorder (PTSD) symptom severity, satisfaction with life, and reintegration difficulty at baseline right before writing, and 3 and 6 months after the expressive writing intervention. The expressive writing samples were coded for identity disruption using thematic analysis. We hypothesized that identity disruption would be associated with lower social support, more severe PTSD symptoms, lower satisfaction with life, and greater reintegration difficulty at baseline. Forty-nine percent (n = 121) of the sample indicated identity disruption in their writing samples. Identity disruption was associated with more severe PTSD symptoms, lower satisfaction with life, and greater reintegration difficulty at baseline, and with less improvement in social support. The findings suggest that identity disruption is a meaningful construct for extending the study of identity development to established adult and midlife populations, and for understanding veterans' adjustment to civilian life. (PsycInfo Database Record (c) 2020 APA, all rights reserved).