This study is the first to explore the contribution of different types of teacher regulatory talk--directive, guiding, and autonomy supportive talk--in children's development of self-regulation across cultures. Teacher-to-student talk was analyzed under naturalistic conditions in eight Year 4 classrooms, all situated in different primary schools in England (student N = 25) and Chile (N = 24). Self-regulation was studied by observing students' effective metacognitive monitoring (awareness of errors) and effective metacognitive control (effective control of problems) in a series of 11-13 cube assembly tasks. Mann-Whitney U tests showed that English participants demonstrated higher levels of effective metacognitive monitoring and control, and participating teachers a similar level of teacher regulatory talk across cultures. The function that regulatory talk had in predicting students' self-regulation, however, tended to vary according to culture. OLS multiple regressions revealed that while guiding talk had the same positive effect across cultures, directive talk had a negative effect in England but null effect in Chile, and autonomy supportive talk had a positive effect in Chile but negative in England. These results indicate that it would be valuable to explore further the "culturally adaptive functionality" of teacher talk for students' self-regulation development.