Using data from multiple evaluation instruments to evaluate university teachers' teaching quality has been popular in practice; however, the inconsistency of these evaluation results has not received sufficient attention. This study intended to fill the gap by investigating the main reasons for the discrepancy in teaching performance that resulted from student evaluation surveys and classroom observations of two administrators from the English department in one of the largest universities in Vietnam. Student evaluation surveys (n = 604) suggested that teachers performed better in activities that focused on instructional techniques than when promoting classroom interaction and student engagement. Structural equation models further showed that activities that engaged them in learning and promoted classroom interaction had a strong positive effect on their overall satisfaction with their teachers' performances. However, interviews with administrators from the department revealed the conflicting finding that they felt that teachers whose teaching performance was less satisfactory should focus primarily on instructional techniques.