Objectives We aimed to summarize the clinical presentations, therapeutic approaches, and outcomes of type B intramural hematoma (IMHB) patients with and without type 2 diabetes mellitus (DM). Methods Patients with uncomplicated IMHBs were included between January 2016 and January 2018 and divided into two groups according to whether or not they had DM. Cox proportional hazard analysis was utilized to investigate the risk factors for aortic-related mortality. Kaplan-Meier survival analysis was used to estimate cumulative mortality and aortic-related mortality. Results A total of 149 patients were included and were divided into the two groups (DM group [n=60] and non-DM group [n=89]). Patients in the non-DM group underwent thoracic endovascular aortic repair treatment more frequently (12% vs 2%, P=0.028) and had a higher reintervention rate during the follow-up (9 in 81 patients, 11% vs 2%, P=0.043). There were significant differences between the two groups regarding the aorta-related mortality rate during the acute phase (9% vs 0%, P=0.042) and the all-cause mortality rate (22% vs 7%, P=0.011). Ulcer-like projection (ULP) development (during the acute phase) (hazard ratio [HR], 1.07; 95% confidence interval [CI], 1.01-1.31, P=0.008), C-reactive protein (CRP) levels (HR, 1.92; 95% CI, 1.51-2.49, P<0.001) and MMP-9 levels (HR, 16.82; 95% CI, 7.52-28.71, P<0.001) were associated with an elevated risk for aorta-related mortality. Conclusions IMHBs without DM are not benign and have a considerably high aortic-related mortality rate. ULP development (during the acute phase), CRP levels and maximum MMP-9 levels are associated with an elevated risk for aorta-related mortality.