English speaking proficiency requires more than knowing its grammatical and semantic rules. It also includes the knowledge of how native speakers of one language use the language in the context of structures of interpersonal exchange, within which many factors interact. Critical thinking is the deliberate determination of whether we should accept, reject, or suspend judgment about a claim and of a degree of confidence with which the language speakers accept or reject it. The present quasi-experimental study aimed to investigate the impact of teaching critical thinking on the speaking skill of EFL learners. To this end, 44 male and female intermediate students at Respina Talk (i.e., Iran-Canada) language school with the age range of 20-35 were selected in order to achieve the objectives of the study. According to the obtained results, there was a significant relationship between the promotion of critical thinking and EFL learners' speaking skill. The findings of this study may have some theoretical and practical implications for material developers, EFL teachers, language learners, etc.