The chapter analyses the processes and dynamics behind the deterioration of relations between the European Union (EU) and Russia. The chapter looks at how – despite initial mutual good intentions at the beginning of the 1990s – the mismatch between the level of trust and formally set basis and goals of the partnership led to too high expectations on both sides and the fundamental misreading of each other’s intentions. The problem with the relations between Russia and the West in general and the EU in particular has been that trust has been personality-dependent and not truly embedded in structures, practices, institutions, culture, or mind-sets of people. Reverting back to mutual hostility and enemy-images has thus been regrettably easy. The chapter analyses the consequent cycles of reciprocal mistrust from the points of view of both the EU and Russia. We advocate a multidisciplinary and multi-level approach to trust studies. The case is best explained by combining rationalist, constructivist, and psychological strands of trust theorising.