L2 teachers' written feedback (WF) has been widely researched as one key cognitive factor in students' learning of a new language. Little research, however, has viewed WF as a contextually embodied and socially mediated activity that may be influenced by professional development. We compared five Iranian EFL teachers' WF before and after a professional development program in order to understand how the program may have contributed to reshaping their WF practice. We used activity theory (AT) to analyze marked writing assignments, semi-structured interviews, and teachers' narratives after the program. Analysis revealed that while some teachers featured a transformation in the object, tool, rule and division of labor of their WF activity, others displayed a change only in the object component. Professional development in WF helped EFL teachers reconceptualize their WF, making it more indirect and oriented to content. However, these changes also posed a variety of tensions for teachers. Reconceptualizing WF is a key component in teachers WF practice that should be considered along with other social and individual factors that mediate how teachers decide to provide WF to their learners.