Developments in the Policy Advisory Systems (PAS) literature demonstrate how the traditional models designating key roles for internal public service actors have given way to include a greater diversity of external non-governmental actors in advice provision. This is reflected in how sustained politicisation and externalisation trends impact PAS organisation and actors’ influence, resulting in a more complex national PAS architecture and functioning. This pronounced hybridity of PAS, both in structure and logic, presents challenges for ensuring relevant and quality advisory content and managing its supply and dissemination effectively. This paper highlights the drive for quality and transparency in advice provision and discusses factors influencing developments in Ireland’s PAS, including the broader trends of politicisation and externalisation. The findings are informed by interviews and a survey circulated to Irish civil servants who perform policy worker tasks and are engaged in providing advice to ministers. The research finds that new structural and institutional arrangements introduced to Ireland’s PAS have a created greater capacity for evidence based advice in the internal PAS and a more contested space for policy advice. It also highlights that this has not fundamentally disturbed embedded characteristics of the Irish policy-making environment. Political demand pressures from ministers (both personal and electoral) can drive elements of politicisation within the civil service whereby policy advice is weighted or discarded based on ministerial preferences.