Children of immigrants often enter school with lower language skills than children of native-born parents. In this paper, we analyze the impact of the duration of preschool attendance on the language development from age three to six of children of Turkish immigrants and children of native-born parents in Germany. We investigate whether the impact of preschool attendance differs by familial language use while also considering different characteristics of the preschool context (quality and ethnic composition). Using fixed effects models, we find that a longer time spent in preschool is associated with better German language skills for Turkish-origin children with low levels of German language input at home. This result is very stable across different preschool contexts. The results highlight the importance of targeted interventions at an early age. (author abstract)