Updated project metadata. Understanding the molecular mechanisms of pathological vascular remodeling is important for treating cardiovascular diseases and complications. Recent studies have highlighted a role of deubiquitinases in vascular pathophysiology. In this study, we investigated the role of a deubiquitinase, OTUD1, in angiotensin II (Ang II)-induced vascular remodeling. We identified upregulated OTUD1 in the vascular endothelium of Ang II-challenged mice and showed OTUD1 deletion attenuated vascular remodeling, collagen deposition, and EndMT. Conversely, OTUD1 overexpression aggravated these pathological changes both in vivo and in vitro. Mechanistically, SMAD3 was identified as a substrate of OTUD1 using co-immunoprecipitation followed with LC-MS/MS. We found OTUD1 stabilizes SMAD3 and facilitates SMAD3/SMAD4 complex formation and subsequent nuclear translocation through both K48- and K63-linked deubiquitination. OTUD1-mediated SMAD3 activation regulate the transcription of genes involved in vascular EndMT and remodeling in HUVECs. Finally, SMAD3 inhibition reversed OTUD1-promoted vascular remodeling. Our findings demonstrate endothelial OTUD1 promoted Ang II-induced vascular remodeling by deubiquitinating SMAD3. This study identified SMAD3 as a target of OTUD1 and indicates OTUD1 as a potential therapeutic target for the diseases related to vascular remodeling.