Drawing on comparative institutional theory, this paper examines post-acquisition integration in international acquisitions, which has seldom been examined through this perspective. Based on a longitudinal and comparative study of three blue-chip French acquirers in the UK that shared similar integration intentions but realized those to varying degrees, this paper theorizes this variation in integration outcomes as a dynamic interplay of institutional distance, market structure and power dependencies. Whilst all important, those effects do not equally explain integration outcomes and can only be understood in conjunction with one another. Thus, contrary to a core assumption of institutional theory that institutional distance is consistently a dominant influence on multinational firms' behaviour, the study shows that its effect is varied. It will only become extremely constraining when the market structure is highly localized, and both dynamics combine to make the acquirer largely dependent on the target firm. The study's first contribution is to provide a fuller conceptual understanding of post-acquisition integration. Secondly, it introduces the role of market structure into a politico-institutional framework and, thirdly, it demonstrates complex relationships among three effects located at multiple levels. The results have important implications for the debate about environmental determinism vs multinationals' agency at host-country level.