Recently, historians have begun to illuminate further the role that ethnicity played in integrating immigrants into mining societies. Ethnicity, they show, shaped foreign−native relations in complex ways. Migrant culture and local norms both affected the assimilation process. This essay, focusing on France’s premiere coalfield of Pas-de-Calais during the 1920s, a period of mass influx of Polish laborers, explores employers’ often underappreciated influence over inter-ethnic relations, and it reveals the far-reaching effects of managerial policies. Management’s ethnic paternalism influenced, though often unintentionally, relations between Poles and French miners and officials. Employer strategies to manage Poles led natives to see themselves as distinct from and even superior to immigrants. Beyond the workplace, employers used ethnic notions to attract and control Poles, yet in doing so they highlighted the dissimilarities between Poles and Frenchmen. Ultimately, coal companies reinforced foreigners’ isolation from local society and roused the suspicions of officials, who strictly policed the Polish community.