The decisions made by the designers of mentorship programs impact upon the development of the praxis of the teachers involved. The recent development of online mentoring provides an opportunity to revisit the question of how to design mentoring programs that support the development of a high quality of praxis in the participants. This chapter argues for a broad understanding of mentoring as formally convened, dialogic communities of teachers that include arrangements such as online, peer and group mentoring. It suggests that a high quality of praxis occurs in a space where mentors adopt a critical stance for reflecting upon the intentions behind the technical skills of mentoring. The theoretical understanding of the praxis of mentoring is explored by describing a design-based research project, TeachConnect, that facilitates online mentoring aimed primarily at preservice teachers. The challenges experienced in convening communities within TeachConnect are used to highlight some of the key issues in fostering a high quality of praxis of mentoring in the online space, including the need to balance a fluid adoption of roles within mentorship with the need for well-prepared mentors.