The current study explores the potential of the collaborative reflection of the teacher, colleagues, and students in promoting teacher expertise. To this effect, the authors first created a principled set of checklists on six domains of teacher expertise by synthesizing relevant literature. Then they developed protocols for collaborative reflection. These tools were applied to a middle school English teacher’s reflective practice, involving the teacher participating in stimulated recall sessions of her own classes, writing reflection journals, and receiving feedback from her colleagues and students. The results show that collaborative reflection has high potentials for mediating the teacher’s cognitive and affective changes, leading to behavioral ones. This suggests that collaborative reflection, when relevant institutional prerequisites are met, can take an instrumental role in promoting teacher expertise.