Professional development in pre-service teacher education include practicum where teacher candidates have the opportunity for teaching experiences in cooperating schools. For that, an effective cooperation and collaboration need to be established between schools and pre-service teacher education programs, and between in-service teachers serving as mentor teachers and pre-service teachers as well as between teacher educators and in-service teachers. During this complex interaction, we need to rely on in-service teachers as experienced mentors and their pedagogical content knowledge while making judgements on pre-service teachers' competencies in language teaching. For mutual professional development, pre-service teachers need to receive helpful feedback from more experienced teachers while in-service teachers, in turn, are encouraged to act as mentors for inexperienced teachers. This paper investigates the needs of both pre-service and in-service teachers in order to provide solutions for the problems both parties might have during this symbiotic collaboration. The study adopted qualitative research design. The data were collected through reflective journals and semi-structured interviews with in-service and pre-service teachers. Content analysis of the data illustrated that pre-service teachers had problems mainly with classroom management, appropriate feedback, time management, and teaching strategies. In-service teachers had serious challenges in establishing theoretical background for their comments and needed more guidance in mentoring. The findings suggested that pre-service teachers need more practice opportunities in their way to becoming a language teacher whereas in-service teachers definitely need to improve and update their theoretical knowledge base on current developments in the field. (C) 2016 The Authors. Published by Elsevier Ltd.