Enterprise architecture (EA) is a holistic approach to aligning IT resources with business processes and strategies. EA often bridges several organisational units and departments. This aspect makes it challeng-ing to establish EA programs as the scope, scale, level of detail, objectives, and resources need to be discussed and agreed upon by several units. In this paper, we study how EA programs are institutional-ised in Vietnam’s public sector. We conduct a multiple case study by deriving qualitative data from three provinces with different experiences and backgrounds. The results show how rules, norms, and values change and influence the EA programs and their institutionalisation. Their relative importance also changes as the EA programs proceed. These results may assist researchers and practitioners in under-standing EA implementation and challenges in public sector e-government initiatives, particularly in developing countries.