Solidarity is one of the rights mentioned as a central value in the preamble of the Charter of Fundamental Rights of the EU and it is the title of chapter IV which contains with Art. 27 (workers’ right to information and consultation within the undertaking) and Art. 28 (right of collective bargaining and action) central rights of collective labor law. The protection of the weaker party is the central idea, both in individual labor law and in collective labor law. But to which extent does that include the idea of solidarity? If solidarity would be the basic idea of the concept of collective labor law, this would imply a strong social approach. The following elaboration looks for an attempt of a definition and analyzes the components of solidarity in collective labor law based upon European and German Labor Law, bearing in mind provisions and jurisdiction on trade union rights, collective bargaining, the right to strike and on European and German works councils. Besides a legal analysis, sociological methodology is also applied, when the internal and external dimension of solidarity or the concept of inclusive and exclusive solidarity are presented.