In advanced transition processes sector coupling becomes key to reach net zero objectives. The literature on multi-system interactions addresses the coupling of different systems by analysing how technologies, institutions, and actors connect. Our contribution zooms in on better understanding the concrete activities and characteristics of actors who work to integrate different systems. It is crucial to understand how actors realise the integration of sectors as the coupling represents a major bottleneck in accelerating transition processes. To identify their activities, we build on the recently established concept of transition work, which adapts the institutional work framework for use in the analysis of transition processes and link it to the concept of ‘system entanglers’. System entanglers are actors who connect different systems. Empirically, we apply our conceptual framework to three qualitative case studies of hydrogen-based sector coupling projects within mobility, heating, and industry in Germany. We find that for system entanglers cross-sectoral competencies and learning, as well as fostering between-system links, are key to connect different systems. We identify further key characteristics of system entanglers and discuss how the sectoral context, the constellation of actors in projects, and the self-perception of the respective actors matter.