Objectives To investigate prognostic significance of follow-up CT findings for initially medically treated type B aortic intramural hematoma (IMH). Methods We performed a retrospective pooled analysis of individual patient data, including baseline and follow-up CT characteristics. All enrolled patients were followed up for adverse aorta-related events, defined as a composite of aortic disease-related death and surgical or endovascular aortic repair. Results A total of 238 patients (73.9% men) were included, with a mean age of 58.19.8 years. During follow-up, 83 patients (34.9%) experienced adverse aorta-related events, most of the events (83.1%) occurred within 1 month after follow-up CT imaging (n = 69). In the Cox regression model for predicting adverse aorta-related events, baseline maximal aortic diameter (MAD) (HR = 1.05, p = 0.008), ulcer-like projection (ULP) (HR = 2.47, p < 0.001), changes of maximal hematoma thickness (MHT) (HR = 1.22, p < 0.001), newly developed ULP (HR = 4.44, p < 0.001), and newly developed pleural effusion (HR = 2.46, p = 0.002) were powerful independent predictors. In combined predictive model for 1-month aortic events, baseline MHT >= 11.8 mm (OR = 4.39, p = 0.001), ULP (OR = 3.98, p < 0.001), changes of MHT (OR = 1.46, p < 0.001), newly developed ULP (OR = 9.27, p = 0.002), and newly developed pleural effusion (OR = 3.45, p = 0.015) were independent predictors. Besides, in patients with pleural effusion at baseline, resorption of pleural effusion was associated with adverse aorta-related events (HR = 0.36, p = 0.027) and 1-month aortic events (OR = 0.23, p = 0.026). Conclusions Follow-up CT findings provide strong and incremental prognostic information for initially medically treated type B IMH, which are helpful for risk estimates and decisions-making.