Tolerance is necessary for the functioning of mature democracies where social cohesion is strong. Results from The International Association for the Evaluation of Educational Achievement's International Civic and Citizenship Education Study (ICCS) 2016 show that, on average, European young people tend to be tolerant, but their attitudes towards equal rights for immigrants vary widely within and across European educational systems. In each of the ICCS 2016 European educational systems, young people with higher levels of civic knowledge tend to be more tolerant, while, in contrast, young people with low levels of civic knowledge tend to be less tolerant. Grade eight ICCS 2016 data indicate that in each of the 14 European educational systems, civic knowledge shows the strongest association with tolerance toward immigrants relative to the impact of individual background variables.