In this article, we examine the role of institutional context, organizational structures and trade union strategies in tempering membership decline in the number of trade unions in Poland. Empirical data include membership statistics collected for NSZZ Solidarność and 54 affiliates of two other largest trade union confederations (OPZZ and FZZ) supplemented by semi-structured interviews with union leaders. In a decentralized collective bargaining system in Poland, a centralized trade union confederation (NSZZ Solidarność) can more easily shift resources to efficiently organize workers than decentralized confederations, OPZZ and FZZ, whose development is mostly driven by competing trade unions representing narrower occupational groups. In conclusion, this observation is put in a broader context of the debates about trade union renewal in Eastern Europe.