This thesis explores the Danish labor movement’s use of Twitter during the collective bargaining in spring 2018 from a mobilisation perspective. This is done to investigate 1) the form of contentious politics practiced by the Danish labor movement, and 2) the role of trade unions in the Danish labor movement. One specific hashtag, #ok18, is analyzed. This investigation mainly builds on framing theory as developed by Snow & Benford (1986; 2000) and its connection to the logic of collective action, and the logic of connective action developed by Bennet & Segerberg (2013). Three methods were used to analyze the labor movement on Twitter: a social network analysis of @mentions, semantic network analyses of Twitter streams, and a quantitative content analysis. This study finds that the most important and central actors within the labor movement on Twitter are trade unions. Nothing indicates that Danish public employees used Twitter to organize independently of trade unions. Furthermore, the labor movement used Twitter to articulate collective action frames that served as shared “schemata of interpretation” for the collective bargaining. In addition, several framing processes that changed the collective action frames were identified. These results all indicate that the labor movement’s mobilisation on Twitter during the collective bargaining of 2018 is best described by the logic of collective action. There were no indications of personalization of politics or of an increased symbolical inclusiveness. The successful mobilisation in Spring 2018 might therefore be interpreted, with the big proviso that that this study only investigates Twitter, as the first small steps towards a revitalization of conventional trade union politics in Denmark.