Objective: The optimal treatment of intramural hematoma (IMH) involving the ascending aorta remains controversial. This study aimed to analyze the results of the management of patients with acute IMH involving the ascending aorta and extending into the descending thoracic aorta, to compare outcomes of descending thoracic endovascular aortic repair (TEVAR) with that of medical therapy (MT), and to assess the risk factors associated with adverse aortic events. Methods: We retrospectively analyzed all patients diagnosed with acute IMH involving the ascending aorta and extending into the descending thoracic aorta from January 2012 to December 2019. The primary end points during follow-up were aortic disease-related death and adverse aorta-related events that required surgical or endovascular treatment, such as aortic rupture, the progression of aortic disease, or endoleak. Results: We identified a total of 135 patients with acute IMH involving the ascending aorta and extending into the descending thoracic aorta, of whom 104 underwent descending TEVAR (group 1) and 31 were managed with MT (group 2). Freedom from adverse aorta-related events at 1, 3, and 5 years was significantly higher for patients who underwent descending TEVAR compared with those managed with MT (89.2%, 88.2%, and 84.0% vs 74.2%, 74.2%, and 74.2%, respectively; P=.026). The 1-, 3-, and 5-year survival rates for patients in the descending TEVAR group was 100%, 100%, and 100%, respectively, which was significantly higher than the survival of the MT group: 93.5%, 93.5%, and 81.9%, respectively (P=.002). On a univariate analysis among patients receiving MT, those who suffered adverse aorta-related events showed a higher prevalence of renal insufficiency (55.6% vs 9.1%; P=.003). In MT patients, multivariate analysis showed that renal insufficiency was the only independent risk factor associated with adverse aorta-related events (hazard ratio, 8.691; 95% confidence interval, 2.056-36.737; P=.003). Conclusions: Based on our study, compared with MT, descending TEVAR might be the more favorable treatment for patients with IMH involving the ascending aorta and extending into the descending thoracic aorta. Patients with renal insufficiency are more likely to experience adverse aorta-related events, which implies the need for subsequent intervention or an increased risk of mortality. The risk factor would be helpful for clinical decision-making.