Heritage languages are key to shaping the identity of many individuals who grow up in environments where the dominant societal language is different from their home languages. Yet heritage language learners can be incredibly diverse in terms of cultural and language backgrounds, language proficiency, literacy skills, language socialization experiences and in many other ways. Heritage language education and literacy development, in particular, have been examined in both formal and community-based educational settings. Insights drawn from this growing area of research have informed our understanding of challenges faced by heritage language learners in relation to literacy socialization, such as a lack of educational resources and community support. A subset of this research examines the issues faced by mixed-heritage language families in relation to literacy. This article reports on the qualitative phase of a mixed-method study on the language and literacy socialization experiences of interlingual families in Canada with mothers of Japanese descent. The findings highlight the multiple challenges faced by the participants in relation to the development of Japanese literacy. It draws attention to the complexity of their family lives, and how the promotion of multilingualism in the two official languages of Canada comes at the expense of Japanese literacy skills for their children.