Background: Anatomic remodeling within the thoracic aorta following thoracic endovascular aortic repair (TEVAR) for type B aortic dissection (TBAD) has been well documented. However, less is known about the response of the untreated visceral aorta. In the present study, we investigated the visceral aortic behavior after TEVAR for acute or subacute TBAD to identify any associations with the clinical outcomes. Methods: A multicenter retrospective review was performed of all imaging studies for all patients who had undergone TEVAR for acute (0-14 days) and subacute (14-90 days) nontraumatic TBAD from 2006 to 2020. The cohort was inclusive of those with uncomplicated, high-risk, and complicated (defined in accordance with the Society for Vascular Surgery reporting guidelines) dissections. Centerline aortic measurements of the true and false lumen and total aortic diameter (TAD) were taken at standardized locations relative to the aortic anatomy within each aortic zone (the zones were defined by the Society for Vascular Surgery reporting guidelines). Diameter changes over time were evaluated using repeated measures mixed effects linear growth modeling. Visceral segment instability (VSI) was defined as any growth in the TAD of ≥5 mm within aortic zones 5 through 9. Results: A total of 82 patients were identified. The median length of imaging follow-up was 2.1 years (interquartile range, 0.75-4.5 years), with 15% of the cohort having follow-up >5 years. VSI was present in 55% of the cohort, with an average maximal increase in the TAD of 10.4 ± 6.3 mm during a median follow-up of 2.1 years (interquartile range, 0.75-4.5 years). Approximately one third of the cohort had experienced rapid VSI (growth ≥5 mm in the first year), and 4.8% of the cohort had developed a large paravisceral aortic aneurysm (TAD ≥5 cm) secondary to VSI. Linear growth modeling identified significant predictable growth in the TAD across all visceral zones. Zone 7 had the highest rate of TAD dilation, with a fixed effect estimated rate of 1.3 mm/y (95% confidence interval [CI], 0.23-2.1; P = .022). The preoperative factor most strongly associated with VSI was a cumulative number of zones dissected of six or more (odds ratio, 6.4; 95% CI, 1.07-8.6; P = .041). The odds for aortic reintervention were significantly increased for cases in which VSI led to the development of a paravisceral aortic aneurysm of ≥5 cm (odds ratio, 3.7; 95% CI, 1.1-13; P = .038). Conclusions: VSI was identified in most patients who had undergone TEVAR for management of acute and subacute TBAD. The preoperative anatomic features such as the dissection extent, rather than the procedural details of graft coverage, might play a more significant role in VSI occurrence. Significant TAD growth had occurred in all visceral segments. These results highlight the importance of lifelong surveillance following TEVAR and identified a subset of patients who might have an increased risk of reintervention.