The appropriate scale of metropolitan governance has been the subject of long-running debates. These debates between institutional fragmentation and integration proponents have revolved around the efficiency and effectiveness of metropolitan governance structures. However, the democratic acceptability of such reforms – whether and which citizens support or oppose metropolitan integration – has been largely ignored. This article makes two contributions. First, it develops a socio-psychological explanation of citizens’ support for metropolitan integration. Second, it uses unique survey data of 5000 respondents from eight West European metropolitan areas to demonstrate that group-based (local attachment and nationalist party support) and cognitive factors (exposure to metropolitan issues and heuristics) are linked to metropolitan integration support, while material interests are less relevant. These findings are in line with multilevel governance research more generally and suggest that citizens’ multilevel governance perceptions exhibit similar patterns across territorial scales.