For counsellors and counsellor educators, developing a sound sense of professional identity is a necessity in preserving and advancing the counselling field. In an effort to promote professional identity development in a group of counsellors in training, a co-mentoring programme was developed that paired master's level and doctoral level counsellors. The participants used letter writing and email to support the development of these mentoring relationships over the course of a semester. This study attempted to measure the effectiveness of the co-mentoring programme using interview data and written artefacts. An open, axial and selective coding process was employed. The participants of the study identified themes of enhanced professional identity development and collegial professional relationships as a result of participating in the co-mentoring relationship. Further research is needed to determine how best to support professional identity development for emerging professionals and the effectiveness of mentoring relationships and letter writing in this developmental process. A co-mentoring programme may offer training settings an opportunity for student self-awareness and growth in an experiential and meaningful manner, as well as providing additional opportunities for students to develop their professional identity. Implications for the use of co-mentoring and mentoring programmes to aid in the identity development of counsellors or other professionals are addressed.