In the face of too much incoming information and too many people trying to convince us in today's world, the ability to think critically gains an ever greater saliency as a prime goal of student and teacher education. The present study aimed at substantiating the relationship between EFL teachers' critical thinking ability and their student-evaluated professional success. To this end, measures of the critical thinking ability of 67 Iranian EFL teachers were obtained using the Farsi version of Watson-Glaser Critical Thinking Appraisal, Form A (WGCTA-FA) (Watson & Glaser, 1980) (Faravani, 2006). In addition, their professional success was estimated by their students through the Successful Iranian EFL Teacher Questionnaire (SIETQ) (Pishghadam & Moafian, 2009). The Pearson product-moment correlation analysis indicated a statistically significant relationship between the two sets of measures (r = 0.7, p = 0.05). More specifically, the multiple regression analysis demonstrated that three of the five aspects of critical thinking as defined by Watson and Glaser (1980), namely "drawing inferences", "interpreting evidence" and "evaluating arguments", are significantly positively correlated with SIET scores. Implications relate to the need to accommodate "critical thinking" as an essential aspect of EFL teacher education and teacher evaluation programs, and to readdress the concept of EFL/ESL teacher effectiveness with an eye to teachers' critical thinking ability.