This randomized clinical trial (RCT) tests the efficacy of an emotion regulation treatment, Manage Emotions to Reduce Aggression (MERA), to decrease aggression in Veterans with posttraumatic stress disorder (PTSD) and improve PTSD treatment initiation. Background: Veterans with PTSD symptoms report difficulty controlling their aggression which can lead to devastating interpersonal and societal consequences, such as incarceration, family violence, and disruption of social support. Veterans with PTSD primarily engage in impulsive aggression (emotional, reactive, and uncontrolled) rather than premeditated aggression (deliberate, instrumental, and planned). Emotion dysregulation, or underdeveloped skills in emotional awareness, emotional acceptance, behavioral control, and/or content- appropriate regulation strategies, fully mediates the relationship between PTSD severity and impulsive aggression in Veterans. Additionally, Veterans report fearing their emotions as one reason they do not initiate PTSD evidence-based psychotherapy. Emotion regulation appears to influence both aggression and treatment initiation for Veterans with PTSD. Thus, this proposed study targets emotion regulation with the goal of reducing impulsive aggression and preparing Veterans for PTSD evidence-based psychotherapy. Research Plan: Our goal is to test the efficacy of an innovative emotion regulation training, MERA, with a RCT of 204 Afghanistan and Iraq Veterans with PTSD and impulsive aggression. MERA is provided in three sessions to address logistical barriers faced by younger Veterans who are reintegrating into their communities. MERA incorporates education, cognitive-behavioral and acceptance- based skills training. It also includes information about what emotional experiences to expect from PTSD treatments. Three sessions of present centered therapy will serve as an active control group which is consistent with treatment as usual. MERA and present centered therapy will be compared on changes in aggression from Session 1 to the 2-month posttreatment changes. We predict Veterans who complete MERA will have greater reductions in IA and emotion dysregulation as compared to Veterans who complete present centered therapy. Finally, rates of PTSD evidence-based psychotherapy initiation (attend 1 session), will be examined via a chart review 6 months post treatment. We predict Veterans who complete MERA will initiate PTSD evidence-based psychotherapies at a greater rate than Veterans who complete present centered therapy. Significance: This study supports 2 Veterans Affairs missions: reduce aggression and increase PTSD treatment initiation. PTSD is one of the most commonly occurring and costly psychiatric conditions among Veterans. Veterans with PTSD are more likely to engage in aggressive behavior than civilians with PTSD or Veterans without PTSD. Reducing aggression is a critical need for Veterans, their families, and society. Additionally, there are effective treatments that r...