In the 20th century, the eugenics movement in Europe became acceptable for European social work in a number of different contexts. 'City Welfare in the Sway of Eugenics' investigates the municipal youth welfare system in Switzerland based on the guardianship case files and reports of two medium- sized Swiss cities. Our research provides insight into how eugenics is linked to social work activities and practices in various political, economic, and institutional contexts. Our findings reveal how complex and often paradoxical the connection between integration and exclusion in the various fields of social work can be. Crucially, we show that the general principle of integration in welfare was not formulated without any involvement of political programmes. This insight is highly relevant today: amid increasing inequality, social work must be aware of its ambivalent social function in the force file between integration and exclusion. Based on stringent historical research, our article seeks to contribute debate on contemporary social work in the context of ever radical social change.