["Journal of Traumatic Stress, EarlyView. ", "\nAbstract\nRecent research has challenged the assumption that specific emotion regulation (ER) strategies are universally adaptive, emphasizing instead ER flexibility—the ability to adjust strategies in response to shifting situational demands. Contemporary theory conceptualizes ER flexibility as a multicomponent process involving context sensitivity, access to an effective strategy repertoire, and feedback responsiveness. Although ER flexibility is positioned as key to adaptation following traumatic events, empirical work has largely focused on normative, nonclinical samples, leaving real‐world affective benefits in trauma‐exposed populations unclear. Using ecological momentary assessment, we examined momentary associations between ER flexibility components and momentary psychopathology symptoms in 64 trauma‐exposed U.S. veterans (4,371 observations), including 27 who met posttraumatic stress disorder (PTSD) diagnostic criteria. Participants completed four surveys per day for 21 days assessing emotional situations, situational characteristics, ER strategy use and change, and momentary symptoms. Multilevel models tested within‐person associations between flexibility components and symptoms and examined whether effects differed by PTSD status. Higher context sensitivity, β = −.09; repertoire use, β = −.05; and feedback responsiveness (strategy switching and initial effectiveness interaction), β = .10, were independently associated with lower momentary psychopathology symptoms, ps < .05. Within feedback responsiveness, ps < .01, maintaining initially effective strategies was associated with lower anxiety, β = .27, whereas switching from ineffective strategies was associated with lower depression, β = −.17. Associations did not differ by PTSD status. ER flexibility supports adaptive emotional functioning in daily life among trauma‐exposed veterans regardless of PTSD diagnosis, highlighting its potential clinical relevance as a transdiagnostic process.\n"]