This study aimed to examine the effects of English teacher misbehaviors on students' perception of teacher credibility. Three hundred and ninety-eight participants completed a Taiwanese Teacher Misbehavior Scale (TTMS) and a Student Perception of Teacher Credibility Scale. The Pearson's correlation coefficient (r) was computed to examine the relationship of English teachers' four types of misbehavior shown in TTMS: derisiveness, incompetence, irresponsibility, and non-immediacy with students' perception of teacher credibility. The results indicated that English teachers' misbehaviors were correlated negatively and significantly with students' perception of teacher credibility. In addition, the ANOVA test revealed statistically significant results as well. A further MONOVA was computed to examine the effect of interaction among all variables. Results of the analysis of variance revealed two types of teacher misbehavior-incompetency and non-immediacy-best predicted teacher caring, out of the three dimension of teacher credibility. However, there was no significant interaction found on the other two dimensions-competency and trustworthiness. Further discussion and pedagogical implications were addressed.