Abstract This study explores the extent to which first language (L1) versus second language (L2) use and attachments to native versus majority language and culture influence the proficiency in the L2 Dutch among the Turkish-Dutch bilinguals. The community under investigation is of particular significance because it represents the largest non-Western ethnic group in the Netherlands and it has often been discussed in the context of the group members’ ethnic and linguistic attachments as opposed to their perceived unwillingness to adopt the cultural norms of the Dutch society. What makes this immigration setting interesting is that the shift from tolerance to startling levels of restrictiveness in policies of cultural and linguistic integration has nowhere been as fast as in the Netherlands. Data are collected from the first generation Turkish immigrants (n = 45) who migrated to the Netherlands after the age of 15 and lived there for 10 years or longer and native Dutch speakers (n = 39) via an elicited speech task, a lexical naming/recognition task and a sociolinguistic background questionnaire. The first set of analyses reveals several links between the individual variables (i.e., L1 use in the family and with friends, L2 use at work, level of education, length of residence and cultural preference) and different aspects of L2 proficiency. However, the effect sizes of these correlations are weak to moderate. The second set of analyses applies a discriminant analysis where proficiency in the L2 has been established as one integrated score. In this analysis, only preferred language emerges as the best predictor of language development.