Moyamoya disease (MMD) is a chronic occlusive cerebrovascular disease with unknown etiology. Recent genetic studies have identified RNF213 as an important susceptibility gene for MMD. To evaluate the role of RNF213 in vascular remodeling, RNF213 knockout mice (RNF213-/-) and their wild-type littermates (WT) were subjected to common carotid artery ligation to induce vascular hyperplasia. We examined the vascular expression of matrix metalloproteinase (MMP)-9, known to be increased in MMD. MMP-9 expression was significantly higher in RNF213-/- mice than in wild-type mice 1 and 7 days after common carotid artery ligation. The vascular wall was significantly thinner in RNF213-/- mice at 14 days. The increased vascular expression of MMP-9 and subsequent vascular wall thinning in RNF213-/- mice could reflect the early characteristic of MMD, consistent with the recently proposed constrictive remodeling theory.