In Western cultures, subjectivity has often been seen as the "black sheep" of educational research because of its heavy emphasis on objectivity. Consequently many research initiatives in education share the assumption that objective reasoning should play a central role. However, mentoring teachers' practice improvement research often requires us to go beyond the objective dimension and encompass the subjective dimension of the research process such as teachers' intuition, tacit knowledge and personal meaning-making. The challenge that lies in front of us is how to mindfully make sense of the role of subjectivity in teacher expertise development. This paper examines this issue in terms of three case studies of in-service teachers' action research projects and points to what it takes for us to mindfully embrace subjectivity in mentoring teachers' practice improvement research.