Background: This study evaluated the effect of residual arch tears on late reinterventions and arch dilatation after hemiarch replacement for patients with acute DeBakey type I aortic dissection. Methods: Between January 1995 and October 2018, 160 consecutive patients who underwent hemiarch replacement for DeBakey type I dissection were retrospectively enrolled. They were divided into patients with (n = 73) and without (n = 87) residual arch tears. The arch tears group was subdivided into the proximal/middle arch (n = 26) and distal arch (n = 47) groups to evaluate arch growth rates according to the locations of residual arch tears. The endpoints were arch growth rate and late arch and composite events. Results: The arch diameter increased significantly over time in patients with residual arch tears (1.620 mm/y, P < .001). The increase occurred more rapidly when residual tears occurred at the distal arch than at the proximal/middle arch level (2.101 vs 1.001 mm/y). In the adjusted linear mixed model, residual arch tears or luminal communications at the distal arch level were significant factors associated with increases in the arch diameter over time. The 10-year freedom from late arch and composite event rate was significantly lower for patients with residual arch tears than for those without (82.4% vs 95.5%, P = .001; and 68.0% vs 89.3%, P = .002, respectively). Conclusions: Residual arch tears are significant factors associated with late arch dilatation and reinterventions, especially for patients with distal arch tears. Extensive arch replacement during the initial surgery to avoid residual arch tears may improve long-term outcomes.