Ministerial cabinets hold a central place in the Belgian politico-administrative system, carrying out the bulk of policy formulation. However, they do not operate in isolation and rely on other actors of the policy advisory system for information supply and advice. They request, receive and use various advisory inputs. This article investigates how ministerial advisers utilize policy advice when they formulate policies. Based on a unique survey targeting ministerial cabinet members, it shows that policy advice utilization varies according to the source and its location in the policy advisory system. The sample consists of ministerial advisers from 11 ministerial cabinets in the two Belgian federated entities’ governments of Wallonia and the Wallonia-Brussels Federation. Ministerial advisers still predominantly use advice from the civil service, which points to the continued importance of advice provision from internal, in-house sources. However, advice from external actors – such as trade unions, civil society or consulting firms – have been observed to have rather high repercussions on policy formulation activities too. Advisory bodies appear to be very much active in supplying advice, but this same advice does not yield comparatively higher utilization scores. Points for practitioners This study focuses on policy advice utilization by members of ministerial cabinets in Belgium, especially when they formulate policies. It shows that internal, in-house sources remain important advice-providers and their advisory inputs still abundantly feed into the policy work carried out at the level of government. However, this article provides evidence that external sources might also supply advice that directly finds its way to decision-makers working in ministerial cabinets and that have considerable repercussions at that level too. This is the case for advice from trade unions, (organized) civil society or consulting firms, among others. Quite importantly for practitioners, our results suggest that ministerial advisers ...