In this qualitative study, we designed an online mentoring program to complement school-based mentoring to enrich the quality of existing mentoring experiences and explored the impact of this project on the professional development of 12 EFL pre-service teachers in an English-medium university in Turkey and six qualified English teachers. Pre-service teachers were assigned online co-mentors and asked to send them their lesson plans and teaching videos and several questions regarding their practicum, lesson plan preparation, delivery, assessment issues, as well as career-related concerns via e-mail to receive feedback. The data collected via semi-structured interviews before and after the project were analyzed through content analysis. The findings indicated a relatively high level of satisfaction among pre-service teachers regarding detailed feedback provision, the development of alternative viewpoints into teaching, enhanced teaching self-efficacy, reduced teaching anxiety, new insights into their career choices, and some challenges concerning the online nature of the study.