The processes of formulation of language policies have not been researched thoroughly. This paper aims to explore the relationship between ideas, power and agency in language policy-making and specifically with reference to the formulation of language-in-education policy for multilingualism in Ireland. Through an argumentative approach to language policy and using a discursive institutionalist framework, the paper examines data from policy documents and interviews with policy actors in the Department of Education and Skills. The paper reports on the ways in which agentive discourses are constrained and enabled by institutional structures. The analysis shows how power resulting from asymmetric internal forces and the hierarchical architecture of institutions prevailed over the capacity of some actors to promote their ideas through discourse. Moreover, it shows how static ideational elements are powerful structural constraints on agency. The paper argues for a conceptualisation of actors in policy-making as agentive individuals who engage in a dynamic struggle over ideas to realise complex and changing policy goals. It concludes by claiming that a focus on discursive forms of power in the policy analysis at the so-called macro level would be beneficial for language policy scholarship.