This classroom intervention study investigated the effects of biliteracy instruction on Grade 2 students’ morphological awareness in French and English. Three pairs of partner teachers (French/English) participating in a professional development project co-designed and implemented biliteracy tasks across their French and English classes, which together comprised a total of 80 students identified as dominant in either French or English or as French-English bilinguals. The biliteracy instruction integrated a linguistic focus on derivational morphology with a thematic focus on illustrated storybooks. Before and after the intervention, separate measures of morphological awareness in French and English were administered to a subsample of their students (n = 45) as well as to a comparison group of students (n = 20) not receiving the instruction. The experimental group significantly outperformed the comparison group in French, but not in English, yet when students’ language dominance was accounted for in the English measure, English-dominant students in the experimental group significantly outperformed their counterparts in the comparison group.