Teacher self-efficacy beliefs, epistemological beliefs, and beliefs about teaching with technology are regarded as crucial factors for teaching mathematics with technology. However, there is a lack of research that investigates these beliefs while taking into account the multidimensionality of the constructs. In this cross-sectional study with n = 198 upper secondary in-service teachers in Germany, we used multidimensional scales to measure teachers' i) beliefs about teaching with technology, ii) self-efficacy beliefs, and iii) epistemological beliefs. Furthermore, teachers were asked to self-report on their iv) implementation of technology with respect to different modes of technology use. The results uncover differential associations among the constructs and identify sub-dimensions that are especially central. In particular, three clusters of sub-dimensions can be reconstructed. One cluster reflects a broader set of sub-dimensions and is related to a more integrated and constructivist implementation of technology. In this cluster, self-efficacy can be identified as a central construct. A further cluster is related to using technology to support multiple representations which turned out to be independent of many other sub-dimensions. Finally, the third cluster comprises sub-dimension that can be interpreted as less central. This cluster in particular contains teachers' beliefs about the detrimental effects of teaching with technology, which points out that beliefs about the risks of technology use are less central than beliefs about the potential benefits of technology. The results can inform more differentiated approaches to teacher professional development related to teaching mathematics with technology.