As an important variable in critical thinking instruction, teacher cognition has been emphasized in recent years, but there is relatively insufficient understanding of how Chinese pre-service teachers perceive the cultivation of critical thinking in teaching English as a foreign language (TEFL). From the perspective of Vygotsky's sociocultural theory, especially the concept of mediation, this paper aims to investigate the cognition of Chinese pre-service teachers about the cultivation of critical thinking in TEFL and the mediating resources concerned. Twenty-four Chinese pre-service teachers were selected from five normal universities. A qualitative approach with semi-structured interview and classroom observation was adopted to seek insights on Chinese pre-service teachers' cognitions about integrating critical thinking into TEFL, and sociocultural theory was used to argue for factors affecting their cognitions. Results revealed that Chinese pre-service teachers understand the connotation of critical thinking to some extent although there are misconceptions, and they are willing to integrate critical thinking into TEFL even though there are many difficulties. Moreover, they perceived that multiple sociocultural factors might be linked with their cognitions, such as previous learning experience, Chinese cultural values, evaluation system, etc. Implications for foreign language teacher education are discussed.