The Interreg Europe (IE) programme supports projects in which interregional consortia develop a set of peer-learning activities, followed by action-plans, aimed at improving given policy interventions. The programme gives priority to projects focussed on instruments in ERDF Operational Programmes that have a direct link to S3. Despite this potential, little attention has so far been paid on exploring systematically the complementarities between Interreg and S3 to maximise policy learning. This paper aims at bridging this gap by framing the relationship between IE and S3 in the broader debate about synergies between different EU funds and stressing the importance of monitoring such complementarities. The present work argues that the Interreg Europe programme can provide a space for experimentation, learning and generation of good practices in S3 that can serve broader purposes. This argument is put forward by describing and analysing an exercise conducted by the Catalan government, which targeted synergies between IE and S3.