This article presents a research and intervention methodology developed in an online continuing teacher education programme. In particular, this article analyses the mentors' professional development processes and the contributions to professional development of their participation in the research group responsible for Online Mentoring Programme (OMP). This programme collaborative research involved an articulated dialogue between researchers and teachers aimed at constructing new knowledge and searching for solutions to concrete practical everyday problems of the OMP. The data revealed that the mentors, in collaboration with the researchers, have been able to critically examine their work with the novice teachers, to develop, implement and evaluate interventions. This collaboration allow the mentors to promote both their own and the novice teachers’ teacher development and construction of new knowledge.