It is well established that European Union (EU) membership and European integration produce path-dependent dynamics. In path dependence (PD) with increasing returns, change is triggered by an external crisis that destroys the existing institutional structure. This exogenous shock opens a critical juncture (CJ), during which a new institutional arrangement is adopted. In light of the historical institutionalist (HI) literature on institutional change, Brexit presents a puzzle: Why would a Member State leave the EU if membership engenders path-dependent dynamics? How can a Member State extricate itself from such complex and long-standing institutional structure in the absence of an exogenous shock? This article examines Brexit through the historical institutionalist literature on institutional change, focusing especially on the critical juncture scholarship. It uses process tracing to analyze Brexit as a temporal process unfolding between 2009 and 2020. The article makes two theoretical contributions. First, it generates new theoretical insights about institutional reform and advances the critical juncture concept. Second, by linking the literature on institutional change with the emerging Brexit scholarship, it also adds theoretical rigor to the latter.