This paper presents the findings of research investigating language maintenance/shift among second-generation Arabic speakers in Athens using adolescents of mainly Egyptian origin and their parents as informants. Quantitative data on language competence and on patterns of language use within Egyptian households indicate language shift in adolescents of the Coptic religion. In contrast, Muslim informants emerge as language maintainers. Qualitative results originating from interviews with parents indicate that the significance of religious practice leads Muslims and Copts to view Arabic and Coptic respectively as core values for their identity. This distinction leads to a differentiation in patterns of Arabic language transmission between Muslim and Coptic Egyptian parents, reflecting both the different internal dynamics of these sub-communities, and their different relationships to the host society.