This study explored the vocabulary adequacy of teacher talk in elementary English teachers’ guides for 4th and 6th grades. Two factors of adequacy, namely diversity and difficulty, were examined for each grade and guide, with reference to the basic vocabulary in the 2015 revised curriculum. The main results of this study are as follows. First, in terms of vocabulary diversity, every guide for 4th or 6th grade was found to use more than 400 vocabulary types, with the diversity index of STTR being higher in the 4th-grade guides. Considering different levels of English between 4th and 6th graders, the 4th-grade guides should provide repetitive use of simple vocabulary, rather than introduction of new vocabulary, to enhance students’ understanding. Second, the analysis of vocabulary difficulty reported that about a quarter of the total vocabulary types in the teacher talk of each guide are classified as high-level vocabulary (e.g., happen, represent), which is difficult for elementary English learners to understand. Therefore, this study took into consideration the vocabulary level of elementary English learners and discussed possible improvements to amend high-level vocabulary. These outcomes provide meaningful implications about the role the guides for elementary English should play in teachers’ use of TEE and suggest the necessity and direction of future research.