Seaports can be meaningfully analysed with a cluster perspective. In this perspective, seaports are regarded as concentrations of economic activity related to the arrival and service of ships and cargoes at ports. This perspective has two main advantages: first, it draws attention to forces of agglomeration and disagglomeration in seaports. Some seaports are able to become concentrations of logistics activities, commercial centres, 'information hubs' and 'shipping hubs', while others do not attract such activities. The cluster perspective allows for an analysis of such processes of agglomeration. Second, the cluster perspective enriches existing theories on governance in seaports. The analysis of governance in seaports has mostly been limited to the role of the port authority. Notwithstanding the central role of port authorities in ports (port clusters), we argue that a port authority is one 'arrangement' to improve the governance in clusters, but not the only 'arrangement'. Other arrangements include the formation of associations, the development of public-private partnerships and the use of networks. The literature on governance in clusters provides a broad analytical framework. This framework has implications for analysing the important and complex issue of the role of port authorities in seaports. In this paper, we deal in depth with the issue of cluster governance in seaports and illustrate our approach to cluster governance with an analysis of the port of Rotterdam.