IMPORTANCE: Compared with older patients, young adults with a history of myocardial infarction (MI) tend to have a higher burden of psychosocial adversity. Exposure to early-life stressors may contribute to the risk of adverse outcomes in this patient population, potentially through inflammatory pathways. OBJECTIVE: To investigate the association of early-life trauma with adverse events and examine whether inflammation plays a role. DESIGN, SETTING, AND PARTICIPANTS: This cohort study included patients aged 18 to 60 years with a verified history of MI in the past 8 months from a university-affiliated hospital network. Baseline data were collected from June 2011 to March 2016, and follow-up data were obtained through July 2019. Analysis began September 2019. EXPOSURES: Early-life trauma was assessed using the Early Trauma Inventory-Self Report short form (ETI-SR-SF), both as a continuous and as a binary variable at the threshold of a score of 7 or higher. Inflammatory biomarkers, interleukin 6, and C-reactive protein were obtained at baseline. MAIN OUTCOMES AND MEASURES: A composite end point of recurrent MI, stroke, heart failure hospitalization, and cardiovascular death over a median 3-year follow-up. RESULTS: Of 300 patients, the mean (SD) age was 51 (7) years, 198 (66%) were African American, and 150 (50%) were women. Compared with participants with MI with an ETI-SR-SF score less than 7, those with a score of 7 or higher had higher levels of interleukin 6 and C-reactive protein at baseline. Compared with participants with an ETI-SR-SF score less than 7, those with a score of 7 or higher were at a greater risk for adverse outcomes, with a hazards ratio of 2.3 (95% CI, 1.3-3.9). Results remained consistent in multivariable analysis. Further adjustment for C-reactive protein rendered the results no longer statistically significant. Early-life trauma displayed a dose-dependent response when analyzed as a continuous variable and by quartiles. CONCLUSIONS AND RELEVANCE: Early-life trauma is an independent risk factor for adverse outcomes in young and middle-aged individuals with a history of MI. Neurobiological mechanisms leading to lifetime activation of systemic inflammatory cascades may be implicated.