The article offers an explanation for variations in the effectiveness of trade unions to obtain legislative and policy concessions in peak-level tripartite negotiations in post-communist East Central Europe. It shows that standard interpretations for such variations—focused on structural legacies, modes of transition, political cycles and institutional differences—cannot account for the problem at hand. Instead, I argue that the sources of these variations are to be attributed to distinct paths of state–labour relations, which are the product of continuous strategic interactions that crucially depend on power dynamics between the main actors. To present a mechanism through which these paths evolve, the article sketches a model of government–union interactions that combines institutional and behavioural variables. I propose a set of hypotheses regarding the conditions that determine initial choice of strategies and factors that influence continuation or modification of these strategies later on. By analysing the cases of the Czech Republic, Hungary and Poland, the article further illustrates how these interactions shape tripartite institutions in such a way that they start reflecting accentuated power disparities between the contending actors, thereby limiting future choice sets for weaker actors.