The primary purpose of this study was to ascertain whether the degree to which Korean middle school students perceived their teachers to be credible made a difference in the effectiveness of teachers’ persuasion as a source of students’ academic self‐efficacy. In the contexts of both general school learning and a specific subject of Korean language and literature, social persuasions by teachers were a significant predictor of student self‐efficacy. Students’ academic self‐efficacy, in turn, was a significant predictor of students’ expected final examination scores. Although perceived teacher credibility did not predict student self‐efficacy directly, it interacted significantly with teacher persuasion in the prediction of student self‐efficacy, as determined by the latent interaction analysis. Consistent with Bandura's assertion and our hypothesis, students reported stronger academic self‐efficacy as they perceived the teachers who delivered the social persuasion to be more credible.