The aim of this study is to investigate how and why elementary mathematics preservice teachers' (PSTs) beliefs about TPACK changed during a method course and field experience. Six PSTs were selected purposefully with reference to their different technological and mathematical backgrounds. Participants were interviewed five times (beginning of the study, after workshops, after method course, beginning and end of field experience) and interviews were conducted within the context of Niess (2005) TPACK components. Content analysis was performed with the help of a codebook developed by reviewing TPACK components literature. It has been seen that PSTs had naïve beliefs at the beginning of the study. Workshops, method course and field experience seemed to change their beliefs. Management concerns began to affect beliefs when PSTs' experiences about teaching with technology increased. It was suggested to give more opportunities for PSTs to teach with technology because; it was found that experiences had the most effect on beliefs.