This chapter presents the results of a corpus-based study of teachers’ perceptions of the Vietnamese high-frequency word (HFW) list for foreign learners. The corpus combined journalistic texts and natural conversations to construct frequency lists of 100 and 1000 words. The list of 100 high-frequency Vietnamese words was then evaluated by 41 Vietnamese teachers through both quantitative and qualitative surveys. The results show that teachers rated the top 100 HFW list as a very useful vocabulary resource (M = 5.15/7). Teachers perceived the list as particularly effective for intermediate learners (B1–B2), though they viewed it as less suitable for both beginning and advanced levels. Additionally, according to our findings, teachers strongly favored approaches such as contextual, topic-based, and communicative, supported by visual aids. Classroom observation alone is considered the most widely used assessment method. The results indicate that integrating corpus-based data with teachers’ perceptions will increase the pedagogical value of frequency lists. Overall, the study demonstrates that HFW lists can provide a significant amount of vocabulary, improve vocabulary retention, and provide a linguistically grounded foundation for Vietnamese L2 instruction.