The Interreg Europe (IE) programme, the main interregional programme, promotes and co-funds projects with the aim of improving the results of regional public interventions through interregional exchanges of experience. The programme gives priority to projects aimed at improving instruments in ERDF operational programmes that have a direct link to S3. As such, the programme is designed to open a space for shared reflection between stakeholders and the public sector. 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 on 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 through an exercise aimed at identifying and exploiting synergies between IE and S3, recently conducted by the Catalan government.