Previous studies have reported the influence of professional development (PD) on participating teachers’ identities. However, what goes on in PDs, how and why they shape particular identities require further investigation. This study contributes in this direction by drawing on the notions of practice-linked identities and identity resources to examine how two teachers’ mathematics teaching identities developed following their interactions with the resources offered in a particular PD. We argue that their developing mathematics teaching identities appeared to be linked to their backgrounds and initial motivations for joining the PD, which in turn influenced their selective interaction with resources. Implications for research and PD are discussed.