The emerge of the mobile technologies in education is confirmed by both international (Clarke et al., 2014; Fabian–Maclean, 2013; Marés, 2012) and Hungarian researches (Abonyi-Toth – Turcsanyi-Szabo, 2015; Kis-Toth – Borbas – Karpati, 2014; Racsko – Herzog, 2015). Accordingly more and more tablets – which supports one-to-one (1:1) computing – can be found in Hungarian schools thanks to initiatives of different multinational companies and governmental IT tenders (see KK Szakmai Tanévnyitó, 2018). It is no use of mentioning that teachers have a key role in the application of mobile technology and tablets. As ChanLin (2017) mentions, the teachers’ pedagogical and technological knowledge and attitude of tablet usage is a dynamic process which is influenced by many conditions. The emerge of tablets in education will be mainly based on the teachers’ experiences whether they see advantages of the devices or not (Churchill, Fox & King, 2012). Our research took place in one of the school districts of Budapest (Hungary), where we measured the general digital competences and the mobile-usage competences of the teachers (N=29, nine primary schools) with DigComp framework and with our self-developed online questionnaire. In the research PPC research design was used with an experimental (tablet-user) group and a control (non-tablet-user) group. We hypothesized that after the four-month-long research period both (H1) the general digital competences and also (H2) the mobile-usage competences of the teachers would change. After processing the data, the results are the following: in the case of teachers’ general digital competences we did not find any statistically significant changes between the results of the pre-test and post-test. However, we found positive changes in the mobile-usage competence but only within the experimental group. Paired t-test shows development in “general device usage” (M: from 3,41 to 3,84; t(17)=-2,45, p=0,025), „file and folder management” (M: from 3,1to 3,57; t(17)=-3,3, p=0,004), „multimedia” (M: from 2,48 to 2,95; t(17)=-3,4, p=0,003), together with „educational usage” (M: from 1,62 to 1,83; t(17)=-3,43, p=0,03).