In Vietnamese boarding schools for ethnic minority students, learners use national textbooks, primarily designed to serve the major group - Kinh students. Therefore, representations of Vietnamese people and culture in these textbooks may mainly focus on this group, and consequently lead to unfamiliarity and loss of interest among students (Cunningsworth, 1995). In international contexts, representations of ethnic groups in English textbooks have been found problematic (Bassani, 2015; Kim & Ma, 2018; Yamada, 2006, 2010). In Vietnam, this issue has not received sufficient interest except for only one study into this type of representations by Dinh (2014), who reveals that the Vietnamese culture in old high school English textbooks was mainly of Kinh people. To address this research gap, this study was conducted to investigate the representations in new high school English textbooks and the accompanying teachers’ books. Employing qualitative approach and quantitative approach, with the underlying procedures adapted from the study by Weninger and Kiss (2013), the researchers identified certain problems. Some noteworthy findings are the underrepresentation compared to Vietnamese people and culture, the absence of some groups, and the limited range of contextual topics. From the results, it is recommended that teachers make modifications to classroom procedures and materials, and textbooks designers incorporate ethnic minorities with more diverse topics.