Since teachers are the most responsible ones for integrating technology into their online teaching practices, understanding their attitudes and beliefs is of great importance. This study thus investigated pre-service English as a Foreign Language (EFL) teachers' attitudes and perceived challenges of teaching online language courses. To this end, a questionnaire with three categories on teachers' values and attitudes, beliefs, and communication self-efficacy and one on perceived online teaching challenges with five categories of attitudinal, pedagogical, interactional, supportive, and technical were administered to 100 MA students of Teaching English as a Foreign Language (TEFL) at Iran University of Science and Technology (IUST). Five open-ended questions were also administered to gain more insight into their attitudes and perceived challenges of online teaching. The results indicated that pre-service teachers were interested in online teaching and believed that online teaching could help learners develop their English language knowledge, and that the advances in online information technologies could provide great opportunities for language teaching and learning. The results also revealed that categories on the attitude scale were ranked as communication self-efficacy, teachers' values and attitudes, and their beliefs. Considering perceived challenges of online teaching, Internet connection, lack of teacher professional development courses for effective online teaching, and lack of previous online learning experiences were found to be the most frequent challenges. The dimensions of challenges were hierarchically ranked as technical, pedagogical, interactional, supportive, and attitudinal. The findings could shed light into designing and developing professional development courses for student teachers who are willing to teach online language courses.