This paper will study how the different Belgian parliamentary advisory committees on equality tackled the policy strategy of gender mainstreaming since its adoption by the UN Women’s World Conference in Beijing in 1995. It examines more precisely the parliamentary advisory committees on equality within the federal parliament and the different regional parliaments, analyzing their role in the advancement of gender mainstreaming on the political agenda. It analyzes when and how they picked up the issue, how they framed it, what initiatives were taken, and to what extent they materialized. Special attention is paid to the extent to which parliamentary advisory committees on equality played an important role in the dissemination of the policy strategy of gender mainstreaming. What role did they play in the field: were they an initiating actor, a supportive force contributing to the debate or a conservative force withholding the advancement of the policy strategy of gender mainstreaming. The underlying aim is to account for the differences and similarities within the approaches of the different parliamentary advisory committees on equality within Belgium, both describing them and explaining them, referring to the federal state architecture and its role in disseminating new policy ideas and approaches.