Contemporary infrastructure networks require large investments especially due to aging. Investment opportunities of network-of-networks are often obscured because current scenarios often concern single infrastructure networks. Major barriers to the construction and use of network-of-networks scenarios are institutional fragmentation and the disconnection of scenario-development phases. This paper aims to construct and enhance the use of network-of-networks scenarios through a participatory scenario process. We employed a hybrid-method approach comprising document analysis, Disaggregative Policy Delphi, and futures-oriented workshop for five large national infrastructure administrations in the Netherlands. This approach yielded twelve key infrastructure developments for which 28 infrastructure experts provided future estimates. We constructed seven scenarios through cluster analysis of experts’ quantitative estimates, qualitative direct content analysis of the qualitative data, and a futures table. The scenarios are: Infraconomy; Techno-Pessimism; Safety; Technological; Missed Boat; Hyperloop; and Green. Our results stress the importance of collaboration: desired scenarios are improbable when infrastructure administrations maintain their current sectoral perspective, whereas an inter-sectoral perspective may generate more investment opportunities. However, these network-of-networks investment opportunities do not simply emerge from network-of-networks scenarios; reasons include administrators’ prevailing conception that sufficient optimization capacity remains within their own networks, and that no common ground exists that helps to overcome institutional fragmentation.