Co-production is now the gold standard in policymaking, characterised by national and international actors with different types of knowledge working together to contribute to a collaborative decision-making process. The benefits of co-production in policymaking can include improved knowledge generation that merges practice-centred, political and technical knowledge and incorporates local knowledges to provide complementary information and increase ownership over policymaking processes. Nevertheless, it can also present pitfalls such as multiple and diverging interests, incomplete and asymmetric information, and resource asymmetries and elite capture as highlighted by Bender in (Eur J Dev Res, 2022). By reviewing a case in the European periphery, we document and illustrate situations of collaboration and conflict, benefits and pitfalls resulting from policymaking co-production, throughout recent Portuguese history and in present-day participatory budget initiatives. From competing national actors to influences from the Global North and Global South, the final outcome reflects a learning process in collaboration but also underlying power struggles.