In this article, we investigate what kind of institutions affect bank ownership transformations in a post-transition economy. We use statistical data concerning mergers and acquisitions in the Polish banking sector over the thirty years since the political transformation. Our results indicate the significant role of political and cultural institutional dimensions in stimulating ownership transformation. The importance and current deficits in explaining Polish banking ownership transformations are evaluated through institutional analysis, emphasising the path dependence role and the critical junctures that influence the development of institutions. Identifying which institutions matter the most is crucial for post-reform economies when selecting the most effective policies. Classification codes G21, G32, G34