To enable the Vietnamese youth to join the international workforce during ASEAN integration, teaching English in general education has undertaken a reform to aim for intercultural communicative competence instead of communicative competence. Since building learners' intercultural communicative competence requires their personal engagement in social interaction, teachers should follow a proper approach to activate students' participation in intercultural communication. This research studied to what extent upper secondary school teachers perceived and practiced intercultural integration prior the educational reform. Data collected from 101 participating teachers through questionnaires and open-ended questions proved that (1) teachers had good understanding of intercultural integration, but (2) they rarely conducted intercultural activities in practices, and (3) teachers' graduate education, not international experience or coursebook teaching, had a positive impact on their intercultural teaching practices. The findings suggested that educational management should be consistent with the progressive reform through the synchronization of all curricular factors towards intercultural education, and teachers should be oriented with intercultural teaching pedagogy to conduct suitable activities to develop students' intercultural communicative competence.