This study evaluates the implementation of a B1 English course delivered through a Learning Management System (LMS) within a blended learning model at Vietnam National University, Hanoi. The research aims to examine lecturers’ and students’ perceptions of the course in terms of content quality and instructional design, and to identify areas for improvement to enhance learning effectiveness. An explanatory sequential mixed-methods design was employed. The quantitative data were collected through questionnaires from 267 students and 71 lecturers who participated in the course, followed by qualitative feedback from responses to open-ended questions to provide further explanation of the survey results. The evaluation framework focused on two key dimensions: course content (consistency, accuracy, and completeness) and instructional design (learning objectives, teaching process, teacher support, and assessment). The findings indicate that the course was generally evaluated positively by both groups. However, a notable perception gap was identified: the lecturers reported very high levels of satisfaction (mean scores around 4.3–4.5/5), whereas the students rated most aspects at a moderate level (approximately 3.7–3.9/5). The students’ concerns were mainly related to the integration between online and face-to-face components, the level of interaction on the LMS, workload, and the need for greater learning support. The study highlights the importance of pedagogical integration and learner support in the effective implementation of blended learning. The results provide empirical evidence for improving LMS-based courses and offer practical implications for the large-scale deployment of blended learning in higher education in Vietnam.