In this paper I examine similarities and differences between the required knowledge base of teachers of English as a second language (ESL) and French as a second language (FSL) for teaching in Kindergarten through Grade 12 programs in Canada. Drawing on knowledge base frameworks in language teacher education (Freeman and Johnson, 1998; Richards, 1998) I discuss how a variety of factors impact the knowledge for language teacher education programs. These factors include the linguistic and cultural backgrounds of teacher candidates in ESL and FSL programs, the different student populations, and the variety of language teaching contexts. Teacher candidates' English or French language proficiency, their personal experiences and understanding of language development, as well as their understanding of real life experiences of ESL and FSL students, impact the development of their knowledge base. I discuss the implications of such nuances for policy and practice in language teacher education programs across Canada. (Contains 1 table and 5 footnotes.)