Digital natives are now of age and comprise the new generation of early career teachers (ECTs). This is an important change in teacher demographics given that new technologies have been introduced into classrooms with expectations that teachers embed them effectively into the teaching of mathematics. This paper draws on the data of three separate studies and reanalyses it to explore how a small group of four early career primary school teachers use information and communication technologies (ICT) in their teaching of mathematics. Two of the ECTs were observed using interactive whiteboards in their mathematics teaching, and two were observed predominantly using tablets. Two important variables developed from the research presented in this paper suggest that ECT's uses of technology to teach mathematics may not be without complications. First, the teachers appeared to experience "device conflict", in that the type of device and its particular affordances and limitations were the primary factors that influenced their mathematics. This was particularly evident in the uses of fixed and mobile devices. The interactive whiteboard (IWB) did not pose pedagogical challenges to the ECTs as their stable location facilitated the opportunity to still use these devices in traditional teaching ways. However, tablets did pose a problem because of their mobility and the need to reconfigure the organisation and to some extent the roles of teacher and student. The second finding was that the teachers' mathematical knowledge for teaching appeared to be directly related to the ways they used their technology.