ABSTRACT: This paper analyses the drivers and constraints for effective cross-sectoral collaboration in river basin management and the extent to which factors identified in related literature determine success or failure of collaboration in selected case studies. Cases selected were from industrialized and densely populated catchments, where trade offs across human activities are particularly intense. This article focuses on three sub-basins: one in the Dutch section of the Rhine; a second in the German section of the Rhine; and a third in China’s Zhujiang (Pearl River) basin. This selection, inspired by the work of the EU-China River Basin Management Programme (2007–2012), enabled a comparative analysis on two levels: (a) between the Chinese and the European sub-basins in order to better understand collaborative forms of management in two very different basin governance regimes; (b) between the two European cases in the Rhine in order to assess how collaborative arrangements vary within the same basin. Empirical work enquired into how cross-sectoral collaboration operates in key catchment management processes; what drivers lie behind collaboration initiatives; and whether obstacles hinder the emergence of collaboration. Our findings highlight various mechanisms through which the wider formal and informal institutional contexts, and processes of institutional interplay, influence more proximate factors identified in the literature. Furthermore, our research illustrates the central role that actor networks and the state play in initiating and sustaining collaboration in water management and river basin governance.